. - Management and resources..operate it like a hospitality business with very clear communication with guests and reliable crews both for cleaning and emergencies. - Consider guest amenities, house rules..hot tub..pet friendly etc- TLC.

Yep, its known as a Fix & Flip loan and you can find it on the Lender Finder feature here on BiggerPockets.The term of the loan will generally be less than 2 years and they will usually fund a percentage of the purchase price (I've seen 60-80 percent) and many times 100% of the renovation.It makes sense to have a strong idea of the reno costs prior to applying for any amount with this type of product. 

I also use PayPal and Venmo.Some just deposit directly into my business account.I make it as easy as possible for my tenants to pay me.

This business seems very very shady.

Now, other tax incentives like simple business write offs for expenses to set up the properties as an STR that’s most likely still something you can write off against your rental income gains.

I would start by getting a look at what you're working with - paying for an inspector to visit isn't a bad idea, but depending on how much hoarding was done, it may be wise to remove some of the junk items first so they can give you a more accurate report. 

I have managed my rentals on a very basic spreadsheet (poorly managed) and it is time to clean up my accounting and legal structures.Can anyone opine on a cheap and effective software for the accounting side of the business? 

I've reached general partner status and am growing my syndication business every day. 

Build relationships and don't treat every person as a transaction, and these types of things won't happen to you.We lend to plenty of investors who use the same wholesalers time and time again and don't try to do any of these things because the numbers work for everyone.Build a quality book of business and none of these things will be issues.

Well actually, I have my ideas...