I have credit, additional that is for the emergency stuff that comes up - oh, we need to replace the water heater and didn’t plan for that...

My problem is that I have the credit but I don't have enough capital  $$ yet to do so. 

HELOCS are sometimes harder to obtain, but they are offered up to 90% now in FL, maybe 95% in some states for highly qualified borrowers.However, you can minimize having to sink so much money into "Dead Equity"  by looking at 85% Investment Property mortgages AND where so many so called "Experienced investors" fumble the ball when using a purchase loan is to take advantage of negotiating  'Seller Concessions/ Credit" in the sales price to pay closing costs. 

I am trying to secure a business line of credit for my deal with them.

In 2017, I paid appraisal and credit report fees in 2017 for a rental property that I closed in early 2018 and I put in an EMD on another rental property which was returned in 2018 due to title issues.

One thing I have been keeping my eye out for is information of how to invest into rental properties with bad credit (past mistakes).

Conshe admitted he and his Fiance both have feloniesThey have a Dog (husky)No prior rental history (lived with his fiance's mom)fairly young (27) ProsThey both work (will offer references) (combined they make over 3x the rent)willing to pay asking price (I listed it about $100-$200 more than I thought Id get)He seemed well spoken and maturethey have a 2 year oldHe said his credit score is about 650 (i'll fact check this later)Am I looking for trouble here?

Try the credit unions. 

After the home was purchased with a loan, there was a series of second mortgages and even a line of credit for 300k as late as 2015.

Johnny is going to have to get rid of his lien and clean up his credit in order to get financingThe other option is to fix and flip the property but getting hard $ may still be an issue as many still look at your credit and your experience