20% down - FHA - because I barely made the FICO threshold.

Assuming this is a passive business - meaning you are not materially participating - any cost segregation fueled losses would have no impact on your W-2 income. 

Although they offered an incentive (larger split) to those LPs who participated, I declined because I did not have the confidence in this particular deal or Sponsor that they would pull it through for a profit. 

If you were to partner with another more experienced investor to purchase a short term rental, do a cost segregation, and "materially participate" then you could gain the benefits you are looking for without negatively cash flowing, and you could work out a deal where you maybe only have to materially participate for the first year to claim your tax benefits and then you can act as a more passive investor.

. - You want a separate shell LLC (one that doesn’t hold any asset and is barely properly capitalized), to use for all public interfacing, contractors, tenants, payments, rents, rehabs, repairs, etc.

The federal CARES Act requires a 30 day notice in certain evictions where the property participates in certain federal programs OR the property owner has a federally-backed mortgage.IMO, the CARES act is an unlawful piece of legislation that has poisoned America, but if the above clause is true, it is an OR statement.

Don’t let people tell you that it is impossible to cash out on bare land.

Also the DSCR ratio at 7% cap rate is barely above 1.

The real question is I have someone selling me a property at 350K with a 20K builders participation credit and I will be able to use my real estate license for help with the down payment, is this a good deal ?

Below is a link that describes passive vs active vs material participation.