Also, I have read something about a bigger down payment, but wondering how this works if I were to assume the existing loan? 

Admittedly, if someone put down 25%, they might not cashflow but, other properties are priced similarly or much higher. 

My sister had my parents' house passed down to her in a quick claim deed, which is also fully paid off Zestimate ~$420K, but she does have some "good debt", roof/windows for house $50K and car payments for her car and my mother's $25K= total debt $75K.

I just got notified by appfolio they are shutting down their listing syndication site "Rentlinx."  

I know an investor who purchased a SF for 100k, with 1300 in rent, He put down 35k, Good luck 

And when rates go down, you can refinance.

DSCR loans are based off of down payment, credit score and either actual or market rents so it helps to supercharge an investor's real estate goals and net worth.

I am trying to understand if it makes more sense to take out a HELOC to buy the 2nd property in cash or just use that for the down payment and take out a traditional mortgage.

These can at times offer lower than average 30 year fixed rates, eliminated PMI requirement, lower down payment requirements,  and closing cost credits.

The only challenge when being a full time investor that depending on how much passive income you are generating from your investments that can slow you down in your growth or maybe you have enough to continue at a comfortable pace.