Will an inspector tell the end buyer the systems are dated and need to be replaced? 

We have very nice homes, that we completely remodel (gut to the studs,all properly done and inspected) I was actually told by a sec 8 inspector not to take it personally but they had to find something wrong with my units, or it would appear they were favoring me, and that the justification for the inspection wasn't there.

What about the inspector?

When you first got the properties - I understand they send a property inspector from the housing authority?  

When should i have an inspector to look at it?

Be careful on the purchase, talk to the local building inspector or building official, give them a visit at city hall before you purchase, you might not be permitted to just rehab this like your regular rehab, you  might be forced to install a new hvac/water/power/gas supply lines (this might cost up to 50k) and have the building quake proof.

In commercial, I rely on experts, engineers not home inspectors, Realtors, attorneys and accountants, all are bonded and insured, if they screw up they can pay for it, it's different than residential but the due diligence is much different too.

In parallel, HOA sent an inspector to inspect the damage, but 2nd flr unit already replaced everything up today.

My advice for you would be to hire a home inspector before purchasing.

Do you view the property and have an inspector check it out first?