I used a solo 401k and have zero complaints.My RE investments out perform the stock market.  

The money will cost me about 5-6% annually , so I would have to outperform that with enough meat left on the bone ..

But 90k in the stock market might outperform a rental property.

It has been almost 2+ year and 1 turnover (late post) and it has been consistently outperforming other rentals in that community and we are getting 12-15% cash on cash return.

I have two duplexes that outperform them financially and from the standpoint of my initial time invested. 

The market is much more passive and liquid and at the moment outperforming RE.

You have a good interest rate on that loan and could easily outperform that with a real estate deal, and essentially have your real estate investing help pay off your car by earning a higher rate of return.   

There are new software products coming out on the market next year that will out perform all the software products on the market right now. 

A BRRR/fixer-upper property in a great neighborhood will outperform a move-in ready property in a lower quality neighborhood.

I currently owe about $395k on them.I would love to get a larger building that can out perform what I'm making now.