Most of my kids are now out of the nest and I'm finally in a position to start investing in RE. 

Save what you would have spent, build up a nest egg and then buy another in a year or two or three.

if you have that one finite nest egg to work with & will not be able to quickly keep saving more, then your best option is going to be either BRRRing or gator lending. my opinion!

It gave us a really nice nest egg to roll into our 16-unit apartment complex that we own and manage now. 

Passive income was one of the biggest reasons for my second acquisition, I am trying to build a nest egg for my future self.

Passive income was one of the biggest reasons for my second acquisition, I am trying to build a nest egg for my future self.

Most of my kids are now out of the nest and we looked at downsizing.

We have a good amount of equity in our current home, we have saved a good nest egg in standard investments (that we could tap into), and we do have $100k + in cash. 

one option would be using it to BRRRR enough properties to generate the desired amount of monthly profit in the end. as far as cash vs down payment, if you want to build more wealth over time, i would definitely use debt so that you can buy 'more' ($) real estate. leaving it in index funds isn't a BAD idea, but if you have the resources (time/knowledge) to invest in RE & do it wisely, you will likely come out so much farther ahead. another question here is, how much monthly income are you looking for this nest egg to generate in retirement?

There are a few approaches you can take with these setups, as Zeke mentioned...When I had five rentals in Atlanta, four in Birmingham, and one in Indianapolis, I structured it with one parent LLC and two smaller LLCs nested under it.