You have the capital gain taxes on the backend.

I think in Ohio you can file in small claims court for amounts up to $6k.

Its tax time so 1099/w2 or bank statement.   

For example, did he buy a business vehicle that he depreciates on his taxes over time?

Property taxes ought to also be considered.

So no tax returns, DTI, etc.

So you tax basis will step up to the sale price.Good luck!

Tax free on the gains if your primary residence for 2 out of 5 years.  

One thing to note, is that if you are doing flips in either Solo or SDIRA the IRS is likely to see that as running a business and you could be subject to UBIT (unrelated business tax) which scales up to 37% so it can be pretty hefty depending on the numbers. 

His insurance company has denied his claim.