First, people are taking equity from their existing rentals and purchasing more, allowing them to accumulate properties more quickly.Second, you're looking at replacing your income based on net profit from properties on which you have mortgages.  

I'm more interested in the buy and hold model to accumulate wealth through appreciation and eventual cash flow.

Build up the personal financial position first, with lots of monthly cash surplus from steady jobs and a strong financial base of assets accumulated over many years.

Can I use cash accumulated in the solo 401(k) to buy her out so that I may get a non recourse loan on the home to free up more money for investing?

557 units - that should allow plenty of space for whatever toys you might accumulate, and still have plenty of units left over for some cash flow to boot.Nice!

So, if I invest $139/month at 9%, I compute it takes almost 26 years to accumulate $169,600 to pay off the note.

However, some of these syndications have themselves been offered on crowdfunding sites, so it's not a black-and-white distinction. 2) experience: some of the most experienced sponsors (more than one real estate cycle in the current strategy) will not be found on crowdfunding sites because they have more than enough investors that they have accumulated over time to fill their deals.

., will I be able to accumulate enough investments to carry me through my retirement years.

The two main issues for you are first the time line crunch, and second that you are wanting to start cashing out not continuing to accumulate.  

I've read Biggerpockets' posts on it, and listened to most of your podcasts, but still not seeing a clear path forward, so looking for all y'all's input to help me understand this aspect of financing.My hunch proposal is a rent-to-own situation, where he still pays on his debt, but my payments pay for the principle, the interest that accumulates on his debt (3.5%), and then offer him 2-3% on top of that, in addition to the $80k to make it to $190k asking price; to be clear, he initially did not want me to pay him interest, but he also does not want to keep the debt in his name, in case something happens to me.