My dear god you guys are good. Every single reply contained a nugget of information--or, in many cases, many nuggets--that I've been thinking about over the past week or so. Discussions with my girlfriend have been happening over this same time, and everything I've learned or been forced to think about resulting from your posts has allowed us to have more meaningful conversations--primarily because I can finally get my thinking at least somewhat straight on this. I'll add details below, but if you want the short version: the current plan is to wait until the spring, when we'll both have to reassess where we're at relationship-wise and, if things continue to go well, we'll figure out a cohabitation plan of some sort. Part of the reason for this is that her roommate may be moving in with *her* boyfriend at that time, and so the approximately eight-month period is somewhat of a negotiation between the *this* fall/winter move-in and then her potentially having to get another roommate to sign a lease (or moving out to find a place by herself). I'm okay with this and in fact feel quite comfortable with everything. The most likely situation is that I move in to her apartment at that time. As someone noted, the rate we'd be charged for her apartment is a few hundred dollars below market value, and so we'd be very hard-pressed to find a better deal. And though a one-bedroom would be cheaper, the thought of not having any space available to myself (i.e., a second bedroom/office) makes the higher, albeit discounted cost worth it for me.
Anyway, some additional thoughts and reasoning below. Apologies if I'm out of sequence or something doesn't make sense.
The mold situation is something that's just come up recently, and I was only made aware of it because of some of my girlfriend's reactions to staying in the place. (She's also really sensitive to things, so bear that in mind, not that it really changes anything.) It's not as though there's mold growing on my bedroom walls, but the air quality in the place may be... not good? Maybe it's in the vents? In the musty basement? About a month ago, I had surface testing done that seemed to indicate nothing was too out of the ordinary, though I'm skeptical of the testing process (and results). I recently purchased a couple of air cleaners that are now spread throughout the house, as well as a dehumidifier that needs emptied every four hours or so. But, I know that these measures aren't enough, and as you can probably tell from my initially dismissive language, I don't know a lot about what should be done. I got in touch with a company about a month ago to come test the air quality, inspect the house, etc. but have since dropped the ball on that. As many of you have noted, I need to take this more seriously than I have up until this point. It's stupid and lazy of me to not have been more proactive here. So: all of the "you need to do something" messages are much appreciated.
There's a chance I may have overstated my penchant for reclusiveness. To be clear, I would much prefer living in the city--closer to work, around young people (my current neighborhood is full of retirees), social sports, etc. Perhaps part of my reluctance to "do things" has resulted from the hassle that it's always been to do them. Knowing that I still have an hour-long commute after a happy hour or soccer game has always been a buzzkill for me. Ceteris paribus, I'll still prefer a night in to a night out and don't plan on changing my lifestyle if I do move into the city, but having an easier go of things when it comes to social activities means that maybe they won't seem as bad (fortunately, many free activities are offered in the city, and I'm not much of a drinker). As someone pointed out in words that really resonated with me (seriously), I've always wondered if my living situation is something more along the lines of "Scrooge McDuck" instead of a healthy Mustache-influenced lifestyle. In fact, there have been quite a few times over the past few years where I considered posting something on these forums along the lines of, "Am I being *too* Mustachian (or stupid) to the point of not 'living my life'?" Sometimes I have a hard time seeing gray areas and view things only in black and white (e.g., if I'm spending money, I'm not saving it--my equations don't always include enjoyment, meaningfulness of the experience, etc.). Dating was always a particular struggle--who wants to travel an hour to hang out with someone in suburbia? And who could be so great that I'd want to travel to hang out with them? So yeah, it's kind of ironic that I now (almost!) let the strange hold of the housesitting situation throw a wrench into a relationship that's somehow developed in spite of it and has become a huge part of my life.
A few other things:
Transportation-wise, my commute is subsidized by my employer. I end up paying about $50 a month to park at the train station (a bus would take an additional half-hour, sadly). Otherwise, I use my car to go to the gym, library, market, and my girlfriend's place on the weekends. By moving into the city, I'd significantly reduce the need for my car to make these daily/weekly trips (outside of a Costco trip from time to time, I wouldn't need it). I'd have to think about it some more to fully crunch the numbers and figure out savings, but it'd certainly be something.
As someone noted re: entitlement, I know that my girlfriend is not the only fortunate person in this story. The rich friend letting me live in his house has undoubtedly been a huge game-changer for me in terms of finances and has allowed me to save far more than I ever could have otherwise. That's not at all lost on me, so I'm hesitant to say I'm "entitled," for that suggests a feeling of deserving things that you don't. In my case, I think I may be hyper-aware and end up being something like the reverse--in other words, I know I don't deserve the cheap rent and higher savings rate that's resulted, and so I'm very reluctant to, I don't know... kick a gift horse in the mouth...? So yes, for different reasons, we're both very fortunate in terms of finances, something that's not lost on either of us. Somewhat related here, for me, there's also the component that I mention above--that my present living situation is not necessarily ideal for me. I'm receiving the cheaper rent, sure, but I'm also making a sacrifice to do so. I'm not sure any of this was worth adding but I typed it out and so I'll leave it in. Ha.
As for the relationship itself, I know there will be compromises to be made moving forward when it comes to finances. One good thing about the relationship, despite what me posting on this forum may suggest, is that our communication has always been really good. She's well aware that saving is important to me and that I prefer staying in. While some couples feel the need to do everything together, I believe we're both better-suited to have a balance that includes more solo (or, in her case, with her friends) activities. By the nature of what I like to do--read, write, etc.--someone who's okay with this sort of balance will be necessary in whoever I end up with. Might it be easier if she were to have a personality and interests more similar to my own? Maybe. Probably? But I guess there also might be something said for me not finding another pseudo recluse and us then suffocating one another. "Go do your thing, I'll be waiting when you get back." Maybe I'm being naive here. Maybe I'm trying to talk myself into something. Maybe. I'm sure to many this may sound like an intended path fraught with peril, but to me it's part of what will be necessary in any successful relationship I end up being in. Does that make sense? Sometimes I'm not sure that it does, which--bear with me here--might be a good thing when it comes to thinking about this relationship. As someone who's risk averse and likes to think he's logic-driven, that it "feels right" to me to try to make this work, despite the potential issues, is a good thing. (I of course may just be bullshitting myself, but I guess time will tell on that.)
The "buying in" to the apartment was a dumb idea. Don't really know where that came from. And the trailer idea wouldn't work for a number of reasons, though I thought that was a good one. There were quite a few other things mentioned that I didn't touch on here, but please do know that I read every post--a couple times, in fact--and really tried to digest everything before coming up with what I hope is the best solution for the current situation.
Again, I can't thank you all enough for your replies and thoughtfulness. Over the past few years, the internet seems to have become merely the place I go to "get mad on purpose," by way of social media, reading the news, etc. So to have feelings resulting from this forum experience be just about the complete opposite of that--gratefulness and hope in my fellow man!--has been awesome, regardless of how things shake out with this. Free advice from really smart people with good intentions. Awesome stuff. MMM Forums 2020.