The contract he proposed is to:purchase the house (20k above their purchase) for 75k.I put 10k into it to fix the roof and HVACHe puts what he estimated as 12k or so to rehabHe believes he can sell for 140k easily FSBO - or use flat rate MLS listingA recent comp nearby (only 1) shows a similar sized, but newer home, much less land, sold for 150k The house needs some new drywall, paint, unsure if tile is still OK, kitchen rehab, 2 bathrooms rehabbed, probably carpet in the roomsMy holding time is 90 days to sell apparently in order to qualify people for FHA loansIs this a good place to put limited supply of my money? 

You can contribute to an IRA from earning income only, and the annual limit on contributions is $5,500.

Located inside city limits within walking distance to shopping and restaurants.

If you don't have the cash to purchase a larger multi family your best bet would be to purchase in some type of group funding.

One way to access your retirement funds to put into your own deal is to take a participant loan from your Solo 401k, the loan is limited to $50,000 or 50% of the balance, whichever is less. 

@Steven Gingerich I think when starting out buying under your own name is the best bet.

Although I have a lot of equity, I'm in the middle of repairing credit - which limits HELOCs and home refinancing - is there an alternative financing that would make sense?

However, Im looking for a loan option that offers limited documentation.

If you’re in Kansas, Nebraska, or Wyoming – your options are limited to non-existent (I don’t mean to denigrate brokers in small markets, but it just isn’t possible to be a specialist and make a living in many areas.

Why limit yourself to just buying the house next door because it just that, next door.