With a purchase agreement, there is typically an option to specify either "liquidated damages" or "specific performance" as the remedy for a failed contract.

And if you actually have a mold issue, you may need to hire an actual remediation company, not just rip some wood out and slather paint over the rest.So first order of business, get the testing done.

I don't have that issue, either, and @Jean Bolger I hope you're able to get it remedied soon... but what prompted me to write was to say how impressive it is to see @Joshua Dorkin 's reply to the concern within 5 minutes!!

You have a day to try to get a remedy.

Can anyone tell me if they have experienced this before and offer some advice or remedy - PLEASE? 

You should also ask for the following if you decide to purchase the property, in addition to all the things Penny mentioned and that normally go along with a residential purchase:Security DepositsIf built before 1978, copies of lead-based paint disclosures given to tenants.If lead remediation or lead abatement work was done, you'll also want copies of all documentation from testing to any reporting required under RRP.  

My period expires Feb 10th and I've had to do all rehab (mold remediation, HVAC, plumbing) out of pocket so far.Knowing now what I've learned, I won't be going that route again.I still have basement waterproofing, drywall, two story deck to go before I can start in on the "handyman" yep stuff (closets, bathroom cabinets & fixtures, replacing missing lights, paints, floors, etc)

The previous owner sold me the duplex and put in writing with my realtor that he would remedy the issue.

Once the deadline is up, seek remedy for holding over.

The only remedy would be hoping that the tenants move so that rent can be adjusted up to market rates.So, yes, it's vital to raise rents every year.