The truth is, you could read 100 books and still not know enough because certain things need to be learned through trial-and-error.

I plan to offer her a mtm lease for 3 months, as to give us a grace/trial period and save me from having a lease start/end in January in upstate NYany thoughts and recommendations are appreciated! 

I'd encourage you to consider a variation of both #1 and #3 immediately.  1) Use FHA loan to buy a nice house to live in that does not need significant rehab.   3) Buy an investment property but spend some time learning how to buy them without 20% down.The reason for #1 is if the house is in good shape, you can save up the monies you would spend on rehab towards a future rent property.  

Our trial date isn’t until Feb of next year, so we continue to sit, receiving no mortgage payments and having increased legal fees.

If this were happening to my Grandma and I presented these facts to a group of unknown business people and they made a bunch of Werther's Original jokes, I would (1) be forgiven for thinking that landlords are the awful stereotypes the media and lawmakers often make them out to be, (2) be justified in hating them forever, (3) also be justified in probably punching them in the face, and (4) probably get away with it because I'd demand a jury trial and as soon as the comments of the punched party got out, the jury wouldn't sympathize with that person either and would let me go.Again, not trying to be the fun police. 

If they miss a payment, then I can red tag the door without a trial.

I am not exactly sure how to phrase my search to best yield the results I am looking.I have tried "modular home financing non owner occupied" and different variations but it is not yielding anything.

I would than apply some creative financing trial offers; subject to, delayed settlement, hybrid offers, partnering with sellers, front porch clauses (this is where the seller pays you money to use as down payments), vertical break up - this is where you offer to buy the building and lease the land (this is a  seller financing techniques)  to mention a few.When I started to solve problems and help others, the universal law of reciprocity would kick in and I started to put together transactions that helped the sellers and me as well. 

Not fun, been there, it is a process of trial and error to get the smell out.  

I can enroll in classes at my local yarn shop or on Craftsy.com to learn to be a better knitter or I can choose to just dig through all of the "free" information available online, or see if a neighbor has time to teach me and be at the mercy of their schedule, and learn by trial and error.