Under bidding, poor quality, not following timelines - those will all kill your project.

Aim for a 620+ credit score, save for a down payment, and research markets with strong rental demand.

@Roy LoganIt sounds like you’ve made some great moves in real estate investing—your BRRR strategy is paying off with those solid returns.At the bare minimum, you should do the following to make your bookkeeping easier:Dedicate one checking account and credit card exclusively to real estate.

I just received an application from someone who meets the income requirement (3x rent) but not the credit rating requirement.

As my wife and I were reviewing it, we saw a few things in the application and on the credit report that looked funny.

Perform the same task in each app to ensure a fair comparison.Load a property with pictures and details.Market that property.See what your marketing looks like from the public's perspective.Submit a fake application to see how easy the process is.Run a credit/screening report on yourself.Enter a maintenance request, assign a vendor, and attach a fake invoice.Enter charges to the tenant's ledger.Enter recurring charges and automatic late fees.Sign documents electronically.Run owner reports.After testing a few apps, one should clearly stand out.

This points to poor management and/or marketing. 

I want to scale, but not sure how to develop my strategy.I have a $200k HELOC and excellent credit worthiness and high income from my day job.

Check with credit union.

There are several benefits of having cash in the bank/liquid reserves versus an open end mortgage (a.k.a) credit card.