I like that you didn't neglect the foundation...so many owners try to rehab in spite of the crawlspace then have problems down the road.Recommendation: Try to avoid steel shims on a pier and beam home, rot/insect resistant cedar shingles are preferred:- allows for more precise leveling- can be easily installed without over driving thicker shims and creating humps in flooring down the road.Congrats

@Jeremy Benezra Yeah, but that's precisely my point. 

There also must be a yield curve of mortgage specific rates that range from 15 year to 30 year but I can't find much information on it.I know that the 30 year treasury can be used as a proxy but I'd like to find something more precise. 

I would  1)  leave rate unlocked    2) get  formally  approved for the  refinance  in order to make sure that all the  details are  acceptable .....once  approved - 3) pay for the  appraisal to  be  done so you know precisely what the value you are working with is  ....once all these  variables are known - watch rates and determine when you want to pull the trigger to lock and close

A 100% tax on land's rental value drops its selling price to zero, with a concomitant effect on HP's, precisely because it transfers incomes back to those that find housing affordable now. 

It all depends on your situation, as well as how precise and fair your asking price is in relation to the market.

I know that many investors buy manufactured housing parks precisely to avoid the cost and burden of owning the home structures.

@Max KarMy advice is to do in depth research on the precise location you want to build.

And be really precise with your rehab costs and ARV.

It really depends on precisely how you reported that rental property on your Schedule E, but one way or another yes the rental income will "count" towards offsetting the mortgage payment.