Does anyone have any advice for people starting out in this competitive field?

As others have noted credit unions are generally competitive on HELOC's. 

Check Furnished Finder, Zillow, as well as AirBnb and VRBO (30+ day stays) to see what sort of competition is in that specific market.

Which do you think will be more competitive, buying from wholesalers or your own referrals?

Moreover, office spaces often face more competition, especially with the rise of remote work and changing demand in the market.On a personal level, I prefer industrial real estate for several reasons.

Alabama is very business friendly and there isn’t nearly as much competition there as some markets.

That means that there is now competition between hosts and you have to give people a reason to book your unit over another hosts.

Since our book, MTRs exploded and got very competitive in some markets.

That’s the kind of agent you want in your corner, especially in a competitive market like San Antonio.While I haven’t worked with him directly, I’ve spoken with an investor friend who did.

It m in the Tampa Florida area and it's very competitive.