Life Situation: 27 years old graduate student (3 years left to a PhD in STEM) who lives with a partner (also 27, wage earner) in a HCOL city. We are unmarried and file singly, but we have mostly joint finances.
Gross Salary/Wages: Combined total is probably a little over $50,000 a year.
I receive a fellowship that works out to about $36000 a year (on top of tuition). I pay taxes on it, but it isn't considered "earned income" according to the IRS. The fellowship also limits my ability to take outside work, though I do have a small side gig for ~$2k a year that goes straight into a Roth IRA. It's more than a typical graduate student would make, though. It also expires in a year, at which point I will be paid for normal graduate student work (TA/RA) and will be getting earned income. Health care is provided for me by the university.
My partner earns a wage, working about 30 hours a week at about $12 an hour. The work is variable and the hours are not consistent. He gets free health insurance from the state.
Taxes: Last year I paid ~$4500 total in federal + state taxes. I don't have my partner's numbers on me right now, but I think he paid less than $500 total. After tax, I estimate that we pull in about $4000 a month, often a little less but sometimes more.
Current expenses:
Average joint monthly expenses, approximate:
Rent is free (thanks university!)
Transportation: $60 (we mostly walk or bike or take public transportation)
Dining: $150
Entertainment: $50
Groceries: $350
Medical: $50
Vacation: $100 (saved up for holiday trips, mostly)
In addition, we each have a "personal" category of $300 each. This money is mostly our way of maintaining some individual control over the budget. Some of it goes to things like haircuts, clothing, fun purchases, but sometimes it goes to paying off loans quicker or saving up for a vacation. I guess the relevant thing for the case study is that there's about $300 a month in our budget that I have zero control over (and I'm fine with this).
So far we have: $1360 a month
Other recurring monthly expenses:
Roth IRA: $458 in his and an average of about $100 in mine
Student loans: paying about $2000 a month right now, but almost done!
Total: ~$3950 a month, but soon to have an extra $2000 a month and no plan for what to do with it
Assets:
Checking + Savings: $17k ($10k emergency fund, $5k is joint savings for something like a vacation maybe (no concrete plans), $2k is personal savings between us from our personal money)
Roth IRAs: $11k all in VFIFX
Liabilities:
Student loans, all mine:
Private student loan: $3k left at variable interest rate, currently 3.75%. Down from about $40k when I graduated. Right now we're putting everything left over into this, and I think it will be gone this month! Finally!
Public student loans: $9k between 6-6.8%, currently subsidized and accruing no interest until I am done with school.
We have a credit card we use for points and such but we pay it off in full every month.
Specific Question(s):
My main question is - what do we do with all our money once the private student loan is gone? Normally I know the answer would be to put the money in tax-advantaged accounts like a 401k, but I don't have any earned income, and my partner is already maxing out his Roth IRA (I don't think his work provides him with a 401k since he's part-time technically? They don't provide him health care either).
Right now we have a few options: I-bonds, buying stocks outside of tax-advantaged accounts, savings account, paying off student loans that are accruing no interest..
To complicate matters, how would the answer change if some time in the next few years we ..
get married?
have kids? (partner would quit work and take care of them full time)
want to buy a house? (not until after my PhD is over and I get a "real job", so at least 3 years away)
I welcome any other advice if something jumps out at you from the case study.