What our clients generally do is take the average gas billing for the year while occupied. give themselves a little wiggle room,  and build it into the rent as a flat rate, similar to water or electric with a single entrance. 

Then refi with my bank for 30 years.

For OO owning it for 2 years of 5 gets $250K gains per spouse of tax free gain.  

She is currently on a one year lease and I have read the requirements for my state. 

Total loan is $500k so the other $400k comes from other investors.My husband invested in a note with Aloha last year as a trial, and unfortunately that one went into default a few months later.

Also, after a year, the mortgage hasn't been paid down by much, especially if it's a 30 year mortgage.The only challenge you may run into is if you purchased it using a low or no money down mortgage option like FHA or VA lending.

sat on the MLS for a year.

I believe it started at $700/mo in the good old days of the recession and is now up to $1000 (undervalue about $150 for that area).

Nothing can guarantee that.Looking back over 30 years and hundreds of deals I can recall only two occasions when a greedy homeowner tried to bail on our deal. 

The building value of the rental is written off across 27.5 years.