I know which product that you are referring to. the conventional mtg product has the following features. 1. minimum 15% down payment 2. 30 yr fixed term 3. rehab and repairs can be included in financing 4. borrower can be a first time investor. 5. no prepayment penalty. 6. the contractor will receive an initial draw at the closing table. 7.

Given some of the issues that we have seen with my mom's old house which is in the suburbs of Pittsburgh I know that costly repairs could be hiding somewhere.

I also currently have 2 rental properties (1/2 of a duplex and 1 SFH) I currently have about $400k in equity in the 2 properties and they generate $2k/mo net income (before repairs)How would you invest this $500k if you had a similar goal as me to reach FIRE status asap? 

Down side the houses in this price range are older and possibly not in best neighborhoods, more repairs possibly harder to find good renters.2.

Also, your realtor should have given you updated sold comps to give you a better idea about what to list your flip for after repairs were completed.

Duplex produces more income, easier to rent, easier to repair and in expensive markets has the potential to appreciate more.  

You inspect, you may need to negotiate repairs or price changes based on your findings, the bank appraises it to ensure they can underwrite the loan, then you close.If you find yourself anxiously waiting, you can do what the vast majority of investors never do: educate yourself on how to manage a rental.

If it was me, once you've repaired it and rented it out, refinance or HELCO the building. 

Termination right if STR no longer allowed, profit sharing, purchase option or ROFR, length of lease and lease options, how to handle major repairs, who pays initial investment in upgrading property, etc.P.S., this is also similar to co-working locations where the operator signs a master lease with the building owner and then rents out cubicles to individual customers.

If you are wanting to buy a primary, make sure your Schedule E on tax returns shows adding back insurance, taxes, repairs, depreciation, etc...