It costs us $40 per tenant.

I heard it cost $100 filing fee so I didn't want to waste money if I didn't have to. 

A FHA 203k Loan is where the purchase price and rehab costs are rolled into a single loan.Assuming you have a respectable FICO you can buy, with a FHA Loan (3-5% down, a 30 year amortization schedule, and a residential loan rate) AND because you closed personally, you will not have Asset Protection, in the form of closing in the name of a LLC/ LLC taxed as an S Corp, or an S Corp.

At this point, instead of continuing to pay the interest loan payments on properties that we will never be able to financially finish since the rehab loans will not cover the actual cost of the rehab, I wanted to know the ramifications of returning the properties to the loan servicer, deed in lieu.

Prepare for additional costs: If you’re adding units, you’ll likely need to address the water meter situation and possibly upgrade utilities.

These properties also offer you the opportunity to perform cost segregations which help with those current taxes. 

Quote from @Charles Evans: You aren't crazy, but you must be honest about the true cost of ownership.

I got the duplex for a very good price so I financed more money than the cost of the house so I don't have to pay for the rehab out of pocket.

Originally posted by @Mark Whittlesey: I would get a UPS Store (or similar) box instead of a PO Box.It costs more but is much more flexible (is an actual physical address, can receive UPS and FedEx etc.)I had a PO Box for a while and got rid of it for exactly those reasons. 

Have you made a research on house prices, rehab costs, time on the market to sell and etc?