If you find a septic designer in your area, they should be able to tell you if the system is adequate for current usage or whether, if any part needs to be replaced, it would need to be upgraded; then you could speak with a septic installer and get an idea of the cost for all or part of the system.  3) Can you control the behavior of the tenants to protect the system (can you prevent them from flushing personal products down the toilet, or pouring bleach down the drain, or washing paintbrushes in the sink)? 

You can literally find answers to all of your questions within the confines of this site.

You can literally find answers to all of your questions within the confines of this site.

You can literally find answers to all of your questions within the confines of this site.

I would need to open my ceiling and flush their toilet and run their sink to see if there's a leak coming from their unit. 

You can literally find answers to all of your questions within the confines of this site.

Do literally everything he said. 

@Aj Parikh There is literally a comment left by you on that post referenced by Jon Parks of you admitting wrongdoing by seeking the interest of your referral kickback over the investor's best interest.

Will they literally tear every wall down inside in order to isnpect everything or will it be a basic inspection for certain safety measures, means of egress etc..Seperately I may have lost zoning due to the lack of previous owners rental license.

I am literally doing a 1031 into Philly as we speak - let's jump on a call if you want.