The market timing of rentals in my area is tremendously important.

you say that you "were told to" get an STR for tax purposes, which seems odd, and that you only have 30-40K... and you might use HELOC money to help with the down payment, which will just put tremendous pressure on you to be profitable and support all of the debt.unless i am missing something i would back up and regroup before you buy a random STR in a random market and hope it supports all the debt you will have to have...

Our brokerage has a tremendous amount of resources that would be helpful.

This comes with time and experience but a book that helped me tremendously (not really a sales book, though) was "Boundaries" by Henry Cloud.The most common challenges for RE Agents early relate to generating leads and focusing on income producing activity.I would consider spending 50-75% of your side-hustle time on income generating activities. 

This experience will a tremendous value to you and your investing career!

Have sold 4 of them at a tremendous profit.  

Also that syndication is a whole other beast, and while there are tremendous benefits from starting a syndication, like taxes, acquisition fees, sharing the work load, etc, the risks are that much bigger.  

It's still relevant, but not tremendously useful for residential properties like this which are valued by comparable sales.

I've done this, and my credit score dropped tremendously (60+ points).  

i think it's because of the tremendous rise in home equity in the past 5 years.i used a HELOC to (1) help with a down payment on a short term loan, that I then paid back in full when I refinanced; and (2) to consolidate some higher interest debt, which I am now paying back by making extra payments against the principal since HELOCs are generally interest only for the first 5-10 years.