Here wood windows ,   which are common in  a house this age are an issue because painted friction surfaces fail the lead inspection for rentals. 

When that happens, you get mold, rot and loss of integrity of those surfaces. 

At this point, and I have barely scratched the surface of learning the neighborhoods, most of the properties I have driven by (due to the attractive purchase price) have been in areas I would hesitate to invest in as they are particularly run down.

On the surface the rent vs the price looks very good

I am barley scratching the surface starting to study this stuff currently still out of work I relocated to Fort Wayne, IN. 

There are three other factor, both very controllable, that also slow or eliminate depreciation:The quality and/or size of the home in the first place;High quality homes use better materials which last longer and look better longer thus increasing the probability the home will hold value.Homes smaller than 16'x80' normally depreciate faster than larger homes because small homes are truly out of fashion (forgive me tiny home advocates) and because smaller manufactured homes look more like "trailers" than a home.The way the land lease community is operated.Well run communities looking to protect the long-term investment of the community over short-term gains almost always stem or slow home depreciation. 

With good communication and an understanding of basic business, there's no reason one business person can't reach out to another in a normal, human fashion.

In summary, it's generally pretty disruptive to normal life, will take longer than you projected, will cost more than you budgeted and unexpected obstacles will likely surface.

Are those solid surface?

There was an economical reason why neither Bush nor Obama enforced illegal immigration laws in a broader fashion.