The interest would be tax deductible due to interest tracing rules. 

Is your DSCR ratio greater than 1-meaning are you cash flowing (according to the lender's criteria of mortgage, property taxes and insurance (and HOA) if applicable).

I then would have my tax cpa enter in or do it after discussing tax based items (depreciation- MACRS, reserves, year end accruals, reserves, etc.).

My duplex - built 1989, 2,060 sf, 2 bed/bath, 1 year old roof, value if I subdivide (county already approved) and sell each separately $150k each ($300k total)Investor duplex - built 1995, 2,300 sf, 2 bed/bath, 5 year old roof, value around $310kThe investors initial request was for an equal trade and they would pay realtor fees, which I replied wouldn't be equal due to buying/selling costs (recording fees, title insurance, closing fee, survey, inspections, loan fees, 1031 fees, accountant fees, repairs), taxes would increase due to new sale price, I'd trade a 3.75% mortgage for a higher one, and I'm on the 10th year of a 30 year loan so resetting that to a new loan would restart amortization and pay more towards interest.

I will give you my numbers since we are 3 years into Velocity Banking.Home was purchased at $410k.Interest rate: 3.125%30 year termMortgage payment is around $1950 (includes insurance and property tax)HELOC: 8.25% Variable rate - current rateCredit Limit: $97kLet's say I made $10k a month and our expenses were $6k each month including the mortgage.

I also want to learn about purchasing properties with tax liens / bankruptcies / foreclosures.1.

Is your DSCR ratio greater than 1-meaning are you cash flowing (according to the lender's criteria of mortgage, property taxes and insurance (and HOA) if applicable).

If my target would be low income residents, are there any grants, tax credits, or funds available to help me with the conversion? 

Owning has advantages that LL does not such as no vacancy, typically lower maintenance/cap ex versus being occupied by tenants, and often property tax breaks. 

I paid tax on it and mowed it about every 5 years so maybe put 10k into over the years.. deductive reasoning suggested city does not build and full blown interchange to go to nowhere.