Every one has a roll in each opportunity.

Is $40k enough to get the ball rolling on any of these niches? 

OPM private investor that bank rolled the rehab and 100% of purchase How did you add value to the deal?

I opened my Solo401k at end of 2018 for the sole purpose of rolling my funds in the next 4-6 years if I decide to leave or during a force reduction.

Account ClosedYou will want to look over the rent rolls in your due diligence phase.

So unless there is a plan for some restructuring you would roll the gains into a new property together. 

Creative financing should up you grown your base of cash flow and equity.Try delayed settlement, with right of possession, subject to mortgagelease optionmanagement with optionwrapssubject toco-sign with owners for equity position - split proceeds and control the deedControl and Roll using auctionsyou know you don't need to buy real estate to profit from it. try to do your investing without going to a lender (to be intimidated and rejected), most lenders are not investor friendly - do your deals with out them!

I personally look at those ads and roll my eyes, but now I might consider that myself.

Should I stock-pile my cash and wait, or get the ball rolling on my real estate empire and start investing asap ?

But if the Real Estate Investing is a side hustle for you then keep rolling the cashflow back into your investing so it becomes compounded.