I'm running the numbers on this, and I'm getting the feeling I might be over-leveraged (not a good feeling!) 

@Derek BennetsenYou would need to check with the crowdfunding provider and/or your tax advisor.A fund that derives its income from 100% investor owned rental property would be passive and debt-free, therefore no tax implications for an IRA or 401(k).A fund that derives its income from leveraged rental property would pass UDFI tax liability to an IRA.  

You can use the power of leverage to secure another rental property, assuming the math works out for you.

Borrowing at 100% leverage has its own risks, but if you're considering one of these packages, I'm going to assume you understand the ins and outs of being fully leveraged, so I'll forego any advice there.Also, to address some comments around the bank selling them, there are regulations in place that do not allow banks to hold a property for profit.  

I'm curious: What's the current leverage percentage/s on your rental/s?

I'm guessing the window is at least 11 years old based on that comment - current modern windows are designed to last 8-20 years...and that's CURRENT technology. 

I want to leverage my experience in the solar  sales industry to get into real estate.

If your loan amount (at 75-80% leverage) is over a million I would look into a small balance Freddie, which is non-recourse.

Even for two complexes with similar style heating systems, I would imagine costs would vary greatly depending on the age/technology of the heating plant. 

The more I educate myself in this game leveraging is starting to make more and more sense for the simple facts of appreciation, cash flow, OPM/banks, & taxes.