I understand that that a home in Jerome Village would already have property tax, that would include additional fees for the roads, infrastructure, etc. and that it's based upon "millage" and the home's assessed value. 

Underwriting will assess the performance and appraisal of the property based on traditional long-term rental comps.

Didn't mean to get political but I generally vote no on anything that will cause more rent control or increase my property taxes (all the special assessments).  

Also, there's the added risk of being compliant with federal regulations & state laws as well as properly assessing/vetting both the borrower and the property.

For example, you buy a house for $1,000,000 but you say you bought it for $100,000How do they find out how much you paid for a house to assess their tax?

I have heard it’s cooled down quite a bit and assessing if it’s still a worthwhile option to consider as a market for str or even mtr? 

Specifically, you should do a deal only because the (complete, comprehensive, accurate) numbers tell you to do so, not because the calendar tells you to.

This could mean investing in property flips or purchasing out-of-state rentals for more stable income, but it would require letting go of the $1,350 rental income from the manufactured home.What factors should I consider for each option, and how would an experienced investor assess this situation mathematically?

If you look at the tax assessment, there will be an assessed value and the taxable value. 

Once you've pinpointed your objectives, it's important to assess your financial situation.