The most obvious is that you will be able to offset your mortgage with renting out a few rooms.

I'm also a mortgage lender.

Digitize physical receipts for easy storage.Additionally, youcan track income and expenses consistently, using software or spreadsheets.I use QuickBooks Online for most of my clients.

I would read the Actual subordination agreement online myself though.

The loan could be secured by the property as a note and mortgage and that way you define the payment structure and interest rate to pay them.

If on average, selling a property costs about 8% So then we would have:200k-8% = 184k - 80 (mortgage) = 104kBut, let’s say the property was a long term holding so capital gains taxes due on it are 15% (assuming no state taxes in Florida  So our capital gain was 100k and 15% is 15k due in taxes!

Primary residence is valued at $1.8m with 10 years and $400K left on a 1.875% 15 year fixed rate mortgage.

A home on a rented lot is harder to sell because of mortgage / borrowing restrictions (educate yourself on local lenders too).

If you cannot qualify conventionally for a HELCO or HELOAN you could try a non-QM second mortgage.  

@Aidan BlackStart your search for a trustworthy house hacking lender by looking at local mortgage lenders who specialize in lending to first-time buyers and real estate investors.