Agreed, last deal I had in Jersey city was lost due to really bad plumbing and electrical issues, on a older mixed use building. 

Will this new wall be required to have electrical service added per code?  

If after adding the additional monthly recurring costs (electricity, gas, water, internet, insurance, lawn care, snow plowing, etc.) to the standard long-term costs (Mortgage, taxes, regular insurance, etc.) the property won't net at least $100 if I can get the average rent I see on FF for that area, then the property isn't worth more investigation.

Be aware of the costs as you'd need plumbing (water and sewer), electric and possibly a separate meter to the new unit.

Few more points:Their lease is valid till May 2025.This is the first time she even told me about mold.In the email she did ask me to settle the lease.I have a little less than a month of rent as security deposit, which I am ready to settle without any additional penalties for abandoning the property.At this point I am okay with her leaving the place, just I want to get the control of the property back to fix the mold issue.History:1) Recently the AC has been replaced and after that there was some intermittent issue with the installation (temp doesn’t reach target intermittently) and I had to call the tech back 5 times to finally get it resolved.2) Also last month I replaced electric range with Brand new Electric range.3) Two months back she said the refrigerator was leaking, I asked her to send picture of the make and mode of the refrigerator, but I never got a reply back.4) Also for last 4-5 months she has been asking me to send her 5-day notice so that she can claim reimbursement, I was sharing a document and she was paying the rent a little late.

Lots of electrical wires still on the poles waiting to service houses that could be built there. 

Electric boat, the navy, Backus Hospital. 

Many carriers have ceased offering new policies or will only accept properties in very nice condition with verifiable updates to the roof, electric, hvac, and plumbing.

I would say look at the big ticket items, roof, foundation, electric, plumbing, HVAC and assess from there if anything needs to be done 

Separately metered gas & electric are generally viewed as more valuable because water is less commonly metered.