Also I shopped very frugal, I would buy a lot of material wholesale or through auctions, and also I had the ability to buy from a former employer, a manufactured housing factory, that was also a huge savings for me.I had to do this deal this way.

You are not crazy :) cap rates on storage got pretty crazy in the last decade as the space has become crowded and money was cheap, starting to see some reversal of that now, but its tough to find deals at a true 10 cap (10 x NOI or NOI / .10).

Fair credit rating starts at 580 not 680 and these are renters not buyers. 

If you just hire the cheapest or first PMC you speak with and it turns into a bad experience, please don’t assume ALL PMC’s are bad and start trashing PMC’s in general.

If they really wanted to save lives they'd let me just install a permanent ladder.

You can easily create your own calculators with AI tools, so save your money.

I don't think they'll make good wholesalers.I know 1 that works at Starbucks now, another started a house cleaning business. 

An STR will look every bit as good as it did when it started - because it has to.Not only that but it is much easier for property managers to get repairs reimbursed when a guest damages something as an STR as opposed to when a long term renter moves out and outside of the security deposit, good luck. 

As mentioned above, check with your town as a starting point.That said, the septic permit will be the challenge. 

Start by reading the Ultimate Real Estate Investing Guide: https://www.biggerpockets.com/guides/ultimate-real-estate-investing-guide/introduction2.