I don't like to increase rent in the middle of the lease, unless justifiable.  

Hard to justify 250 to 300k to purchase a  property. 

A conservative maximum in my opinion if 100K is you're careful with your contractors and get a good deal from a dealer for a new one.I personally would never use a double wide for a rental unless it's used and I get it for a very very low price - they cost more to buy, move, etc and there are not significant rental premiums for them to justify the added cost in my opinion.

or maybe a couple small projects to "justify" an increase in the Tenant's eye?

You have to be able to justify the move.

I personally couldn't justify paying 6% over list price on a rental that doesn't cashflow, but that's because that type of deal doesn't align with my goalsAlso, I'd be happy to look at your underwriting numbers if you send them over. 

It's a question of whether your legal risks justify the cost and the hassle of this setup.

I don't know see how that's a reasonable option unless you sue for medical bills, moving expenses, and other costs that justify paying thousands to an attorney.

I recently had a clients home appraisal come in $15,000 under but it was clearly like size comps to justify a higher price.

All the sudden that starts to justify that extra work of an Airbnb.