For many investors, the bulk of the time and energy input is at the front end when raising their seed capital, and not losing that is the name of the game.

SF from long-time landlords I know, off-market.I would start by casually planting the seed. 

In the beginning your planting a lot of seeds.

We are going to sell one of our duplexes that is really ready to sell with about $20,000 equity for the buyer and will still leave us with some seed money.

We didn't accept, but the seed was planted...

Get enough of a mortgage to give you seed money to start investing.

You need a system that regenerates your seed money so that it never runs out, and the understanding that you NEVER, under any circumstances, SPEND you "seed money". 

People talking about how they grew their business, locked in enough seed capital to fund their business for 10 years, bought their 4th and 5th units.

It is time to rotate some of those dollars out of stocks and into real estate as seed money for this new endeavor.I may be putting the cart before the horse here, as I am looking to try one cosmetic or advanced cosmetic flip to see if it suits me, but given the great fun I have had working with subs on projects on my personal property and my fascination with construction and transforming spaces, I believe that it could easily be something I continue to do.

You may want to pull that extra $20K out if it's your first deal as that is a lot of seed money for the next project, but I would be very careful on doing too many more like that.