(and again I know this is playing the appreciation game which they say not to rely on, and come the end of that 22 years we could be in a down cycle, however I think from this scenario it sounds like for those first 7 years I could purchase enough properties to really dilute the risk.Thanks in advance for any advice!!!

Reading back over my post I realize how bad it sounds especially toward section 8 tenants.  

That sounds like 2 different problems.

Sounds like you might be trying to get into wholesaling.

Also, with insurance there is a difference for actual costs vs. replacement cost.

The hard part for the NOI on the MF is that I think there will be continuous replacement/repair issues.

Like you said, somebody may eventually buy it but it sounds likely that you will have to hold it for several months. 

Sounds great to me all depending on the headache of tenants, location, building.  

So my question is, do you think it is worth to replace the plumbing?

You want the net income after all expenses like, maintenance, utilities, taxes, insurance, property management (if needed), if the property is vacant figure that in, and Cap Expenditures (any big ticket items that might need fixing or replacing once you own), things like the A/C unit, water heater etc.