With completed & documented rehab, no seasoning is available.

The only mention of mobile homes I found is on page 13 of this document classifying them as “residential rental property.” https://www.irs.gov/pub/irs-pdf/p527.pdf 

After that, run the background and credit check, verify their income by reviewing the financial documents they provide, and contact their employer to confirm their employment.

While it’s frustrating that the tenant is still there and not paying, turning off utilities could complicate the situation and potentially lead to legal consequences for your "friend".In the meantime, document everything (the tenant’s non-payment, the lease terms regarding utilities, and their attempts to resolve the issue) to present in court, which may help recover the outstanding balance later.

VTSTRA has a (slightly outdated) list of town ordinances: https://vtstra.org/regs but that does not even get into some of the crazy proposals being tossed around at the state level, like an additional 10% STR tax (atop the 9% M&R + 1% local options tax already in place in many communities). https://legislature.vermont.gov/Documents/2024/WorkGroups/House%20Ways%20and%20Means/Short-term%20Rentals/W~Kirby%20Keeton~Short-term%20rentals%20draft%20language~3-13-2024.pdf

I will however shake a finger at the agent for not reviewing this document with you and teaching you what youre signing.

It cost $200 for all the documents, tax ID, forms necessary for opening the bank account, and a year of support.

If they are allowed to be here legally than they should be able to provide you with documentation to live and work here.

If you are planning to use a DSCR loan, lenders will want to see a valid lease, utility bill, or official document supporting you are living somewhere else. 

Maybe the sellers have documentation to see what the company's name was?