All things being equal, a simpler option would be to terminate the lease with a penalty of one month's rent, agreed to in writing.

Not sure why people go for 40-year fully am instead of just traditional 30-year with 10-year IO option, I tend to think the 40 year term is more of a gimmick

Another option is joining real estate groups on Facebook or LinkedIn.

However, I am unfamiliar with any lenders having traditional mortgage options for anything with a VIN number such as a trailer.

They don't mind higher vacancy rates then SFH might be an option.  

How did the price compare to other options?

Speak with a lender now to understand your options and start building a plan.

I’m not sure a bank would be your best option but it can’t hurt to try.

If I have several options, I would prefer a HELOC with no initial draw requirements (i.e. to establish a literal line of credit that I have no specific short term plans to use), i.e. not something like the better.com HELOC. 

I also want to keep the option open for converting to condo down the road and as long as I am in the apartment doing so much work I might as well.