Just that a 401k/QRP for an owner-only business is able to sidestep much of the complexity to which 401k plans are subject.In other words "Solo 401k" does not describe the type of plan; it describes the type of business that adopts the 401k plan.When you get a "Solo 401k," you're being given an honest description of the limits of the compliance support you'll be getting - adequate for businesses that don't have non-owner employees. 

I just want to make sure that we provide the tenants with adequate notice..PS.

It does indicate the age of the property, so I would check the wiring and service to be sure it is adequate for today's devices.

Keep on scaling with adequate reserves until you hit your point where you no longer want to grow.

But I look at it the other way: be sure that your 100% recap is actually available and provides adequate cash flow to maintain the property going forward.

I thank you for the analysis example, showing that interest rate changes of one or more percent will not necessarily kill a deal if the deal has adequate cash flow in the first place. also the suggestion of umbrella insurance. 

If your retirement utterly depends on having adequate cash flow from your properties, any downturns will cripple you.

The reason I have replaced pipes is so that there was adequate water pressure. 

If you adequately follow the MP rules in IRC 469.

Here is the thing about leverage: everyone has to determine their own level of comfort, but you are really only overleveraged if you are forced to sell low, or cannot produce adequate cash flow to cover expenses.