Crazy way to multiply liability on seller financing.

And Jay you are 100% right sub 2s are very dangerous and having multiply exit strategies available is a plus and need.

So does he give up one source of revenue now, to give him the opportunity to multiply his revenue elsewhere.

Then the home was always used as a residence from time of purchase up until the last 2.5 years or so, which is NOT to be included as "non-qualified use", so the "Home" version should have 0 non-use days by the days owned, making my non-residence factor a big fat 0%, which multiplied by the gain makes my non-qualified use gain another big fat $0, meaning that my gain that is eligible for exlusion is 100%!!!!.......

Divide by 144 to determine monthly expense then multiply by 2 for the duplex.

Multiply $898.82 by 12 months then by 15 years is only $161,787.60. 

Multiply $898.82 by 12 months then by 15 years is only $161,787.60.

Multiply those probabilities by one another, and you have a huge undercurrent of risk ballooning and compounding with each passing month. 

Is there a standard multiplier like say 20% of rent goes to vacancy and opex? 

I believe the one good thing about that spreadsheet is that it can be adjusted by the State you live in. because costs are different in every State the estimate sheet i believe is based on a multiplier for the corresponding State, as most cost estimating books are based. that program does break down a lot of information for you and i think it is a good program, one thing you may want to check is if the program updates every year with current multipliers for the States ( program is probably based on a starting average value for each thing and then the multiplier changes as prices for materials change) and you want to make sure it does that.