Also, the additional income being on the books will allow you to more easily qualify for a loan down the line as well as you will have more documented income.

Books have been written on this topic, and you might find a few.  

Checkout this book I wrote sharing the story.

also when checking employment history-get the number off a website (or phone book), don't use the number they gave you.

I will admit we got pulled into one and to be honest, found what we received through the Bigger Pockets network (tools, books, networking, etc.) far exceeded what we made many times for elsewhere. 

A side note is if in person events interest you - the BiggerPockets conference this year, BPCon 2024, is October 6-8th and is a HUGE opportunity to meet folks, Cody Sanchez the keynote speaker is speaking on buying businesses and "boring" investments like storage units, laundromats, etc and it might be a great place for you to find some likeminded folks https://biggerpockets.getregistered.net/conference-2024/agen...Thirdly, if you're specifically looking for a mentorship program have you checked out some of the reviews and questions on the Guru, Book, and Course Review forum?

I know everyone will be biased toward the strategy they prefer, but I want to hear from those successfully generating income from STR specifically.What books did you read to help you start?

OK, that's another book!

Find a lender willing to put the 137K on their books (or some portion).  

Check out the book "if you can't wholesale after this, I've got nothing for you" and flip w Rick on YouTube (free).