The other component will be how much time and resources you have to devote to finding properties??

Webinars offer a visual component, teleseminars are more familiar to older demographics.

And think of all the ways each of those components can go wrong.

Compared to an IRA, Solo 401k contributions limits are roughly ten times higherThere is no custodial requirement for the 401kYou don't need the additional expense and administration of an LLC to have checkbook controlThere is a built in-Roth component whereas IRAs are either traditional or Roth, not bothA spouse can also participate in the same Solo 401k planThe Solo 401k has additional tax benefits over an IRA when investing into real estate using leverageThe penalties for prohibited transactions are less severe, though it's best not to utilize this benefit :)

Check with your attorney on how to proceed, but I'd be surprised if they told you to close the account to the detriment of your other tenants' payments.

Since that's the only real mechanical components in the building, there's a newer steel roof on the place, and there isn't anything else major that could go wrong; I set aside $15K for it. 

Cash flow is only one component and many will tell you not the most important wealth in real estate happens by value add  forced appreciation and organic appreciation. 

We also use Infusionsoft, which is very capable, but I think it's too expensive and too technical for the average small business person (like $300 a month).We're actually building a solution that will include all the features you mentioned, but it's not out yet, so I'll tell you how I would do it with other companies' solutions.Use Investor Carrot for the landing page component and use Podio for the CRM piece.  

Generally the Landlord remains responsible for only the structural integrity of the building and the major components, like roof and parking lot.  

I realize the new rules say you have to keep PMI for the line of the loan, but since I don't know when you originally purchased, I can't help you decide.You also need to remember the time component of money.