I started the first one in January and going to request C/O next week.

If they do, then you can likely find another tenant for that amount fairly easily, as I would assume the entire town's taxes are up- so if someone really wanted to be in town, that price is the new normal.If your taxes increased that substantially in a C neighborhood, your tenants would way more likely give push back for that type of increase- even though you're not being greedy, you're just imposing the same raise you were given.Often the buyer who had the "well, the numbers are better" mentality is only looking at year 1. 

Not a book, but Bill Faeth has a lot of free, good content on his site and YouTube videos.

So I bought a cheap single-family rental in a C location.

How about a nice picture of your living room or even the front of the house first, followed by the video games?

Find Brandon's videos on YouTube for the "four square" method of analyzing homes and practice.

Most gurus have their clients journey end the moment they send them the money, they join a facebook group - have overseas VA;s moderate it and provide some old videos that get repurposed.Those who are new and thinking they are creative typically get crushed as they are gambling not investing.

What people want in this area of the business (STR) is humans.Look at the top STR coaches and they all say that the more you humanize your listing with personal videos and messages, the more you go up in revenue.

@David C. is absolutely correct. 

Here is a good video The Ohio Division of Real Estate made about wholesaling in Ohio https://www.com.ohio.gov/real/ I recommend you just get your real estate sales license.