If I calculate my actual cap rate after 6 months by using their convention (Subtracting insurance, tax, property management from gross income) numbers match, thus I am getting what was promised on my proposal.

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. 

Now to answer your question, I would avoid multi-family as your starter unless its an amazing deal.

Then your project would be eligible for 20% Federal tax credit & 25% State tax credit.  

Having someone go through the property every six months is vital to avoid deferred maintenance and to ensure that the tenants are following the rules set forth in the lease.

To avoid going through the same poor experience, keep reading.Even if someone gives you a referral here, do NOT make the mistake of assuming that the PMC will meet your expectations, just because they met the expectations of the referral source.In our experience, the #1 mistake owners make when selecting a Property Management Company (PMC) is ASSUMING instead of CONFIRMING.It's often a case of not doing enough research, as they don't know what they don't know!

You will need to work with a tax professional to analyze your current tax situation (income, deductions, activities, etc.) as well as projected income from the fix and flip business.The benefits have to outweigh the costs (payroll costs, additional tax returns, more stringent reporting and compliance requirements, etc.).One important note - an S Corp is not an entity; it is a tax election.

If it is a normal 70/30 leveraged property, you may end up subject to tax on 70% of your returns anyways - so cost benefit, is that 30% tax free portion worth the high tax rates paid and additional filing fees to get tax free treatment on the 30%?

I know the due on sale clause is unlikely to be called by the bank, but don't want to sell with even a small mortgage balance left.Seller finance is to lessen the cap gain/depr recap tax hit.

I do buy and hold single families for cash flow and tax benefits.