Are there other, more cost-effective alternatives to gain similar support and knowledge?

To Sum it up, its a good idea if you can exceed the cost of capital (higher rate than your cost of debt) with what you earn on your heloc/debt you pull out and invest.The question is how much gains above is enough to substantiate the risk of your variable interest rate, well thats up to your personal investing criteria.

Beefing up your portfolio holdings  (even if your individual ownership in the deal is modest) is one of the best ways to gain credibility.

Typically these repairs are mostly cosmetics.

Typically a broker will work with at least 10 DSCR lenders so they should have a variety to reach out for quotes to. 

Start small with a single property to learn the process and scale as you gain experience.This post does not create a CPA-Client relationship.

Also, having a rehab budget already laid out with explanations on how you got the numbers would help and is definitely a plus when I look at deals even though I typically wont use their numbers it at least shows a little more effort. 

Yes you are losing out on market gains but you are gaining appreciation on the property, cashflow from rents, tax benefits, etc..... 

Sounds more like trying to win a popularity contest, aiming to gain votes and likes from people here that also have something against wholesaling.But OK let me play along.Let's fact-check this:OP: "It’ll truly be strange to even hear people and gurus trying to make big money off it."

I wouldn't bet my life on 50%, but I would bet they are more problematic than the typical long-term renter.