Quote from @Carlyn Chism:I agree with Chris on a lender that might be a scam or make you may so much money interest because of the low credit score that you make $1.00 on the flip or no money.  

Seller financed (probably) won't be reported to the credit bureaus and so won't impact your credit score at all.

I am a licensed realtor based in Atlanta, Georgia, and I am currently working on obtaining my mortgage origination license.

So I just rcvd a rental application from Zillow and the credit score is showing 714 which sounds good...

The credit score is the single best indicator of how one pays their financial obligations.

And when you said the management company takes a 550 credit score , all I see in your future are evictions .   

For a $100,000 loan, we would have to charge 2 points ($2,000) for originating the loan.

Turns out that a 520 credit score and a sad story (that turned out to not be true) is really just a 520 credit score.

that we’ve learned in our 24 years, managing almost 700 doors across the Metro Detroit area, including almost 100 S8 leases:Class A Properties:Cashflow vs Appreciation: Typically, 3-5 years for positive cashflow, but you get highest relative rent & value appreciation.Vacancy Est: Historically 10%, 5% the more recent norm.Tenant Pool: Majority will have FICO scores of 680+ (roughly 5% probability of default), zero evictions in last 7 years.Class B Properties:Cashflow vs Appreciation: Typically, decent amount of relative rent & value appreciation.Vacancy Est: Historically 10%, 5% should be applied only if proper research done to support.Tenant Pool: Majority will have FICO scores of 620-680 (around 10% probability of default), some blemishes, but should have no evictions in last 5 yearsClass C Properties:Cashflow vs Appreciation: Typically, high cashflow and at the lower end of relative rent & value appreciation.

It is also important to consider the transactional fees associated with originating the HELOC, whether an appraisal is required etc.