Congrats on your near-engagement!
My two cents:
- Don't combine finances until you are actually married.
- Condo 1 seems unsafe, so sell ASAP. You don't want to live there and don't want to be stuck with a rental in a declining neighborhood.
- You could live in Condo 2, but it depends how attached the current owner is. If super-attached, it will be hard for the new person to truly feel at home and make changs to go from "yours" to "ours."
- Have you considered selling both and renting for a year? When you live together, you'll know how much togetherness you can handle and how much space you'll need. You might consider family planning, job changes, location, etc. and eventually buy a new place together with a huge down payment or pay in full.
- Try to declutter and not need a storage shed when you combine households. You're Mustachian and I'm sure you'll make wise, simple, quality choices.