I do see a ton of 2 unit houses on Zillow, so would it be a good bet that these are landlords trying to unload their stock before student housing regs kick in?

Might be a little bit confused here, but from what it sounds like you were involved in purchasing the property, renovating it and then selling it?

Your best bet is to get an estoppel that verifies their lease dates, rent being paid, security deposit, and advanced rent.

So your best bet is to put yourself in their shoes and shop around just like they would be.Also, some markets are definitely seasonal, and your market rent could change drastically from winter to spring/summer.

I bet if they found a subsurface problem, I would own those. :-)ps.

What financing options are available when partnering with a solo 401(k)? Can you use conventional loans, or does the loan need to be non-recourse?

Your best bet for that size will be local banks and credit unions, good luck.

Kitchens and bathrooms are always a good bet, but think beyond the basics.

It would be a direct sale with no brokers involved. 

Otherwise, rent-by-room is probably your best bet.