I was about to rent out my condo with good cash flow and move back to my mother's house in Central.

Jeremy makes great points.You also have to remember that velocity kicks in. 1st property @ 20% seems daunting, but if you're cash flowing 200-400 a month, that will help considerably with your 2nd property's down payment.

you have a lot of options at that price range. jersey city is big and it is divided into different areas (high level): newport & water front, downtown jersey city, journal square, heights, greenville and bergen lafayette. for your price range, it might not be easy to find a good cash flow place in downtown or newport. you can check out multi family house close to the light rail in the heights; also places in journal square close to path station. also there are some places in greenville or bergen lafayette that have easy access to bus and light rail but you should do more homework if you want to house hack there. it varies street by street. 

I feel like i shouldn't be worried about the estimate because my main priority is cash flow.

I would much rater have a lower mortgage for cash flow than having all of the cash. 

I know tons of investors gravitate towards the northwest side of Milwaukee, and the cash flow numbers on single families always look great.Good luck!

I am interested in learning about how to invest in buy and hold properties with minimum down payment and the ability to own the properties in 20 - 30 years free and clear by renting out and letting the cash flow fund my equity in the properties.

hard money is short term money... and expensive.. not intended for periods of over a year .. interest and points will kill any cash flow investment. 

If so, how does that work with the cash flow?

I've acquired 8 good cash flowing buy & holds in the past year and am about to close on 2 more this month.