You can sell a house with unpermitted work, as long as you disclose it. If you know of unpermitted work and fail to disclose it, you could be sued for fraud. During the sales process, the house will be inspected by a professional inspector who will likely spot any code violations that you will then have to repair. If I were you, I would bring the house up to code as best as possible before selling. If the city will inspect you, great, otherwise, you might want to invest in a professional inspector yourself and avoid any surprises while selling.You should not do work yourself that requires a license, like installing water heaters and hard wired smoke detectors. You are putting the occupants of the home at risk for fire, or worse. You may think you know what you are doing, but you don't know what you don't know. Hire a professional and always get a permit for any work done behind drywall including plumbing, electrical, structural work. Look at it as a free service that will come out and make sure the contractors did the job right. If the contractor tries to talk you out of permits, he is a bad contractor afraid of having his work inspected.
It is an informal classification, so you must contact the homeowner directly.
Yes, it is legal.
Minor foundation cracking and bulging can be normal. However, do not rely on the inspector or the seller's foundation contractor. I would hire my own foundation expert and get a report. You could probably just call several foundation repair contractors and ask for repair estimates and talk to them when they come out. They may say nothing is wrong or that a repair is necessary. A written repair estimate will help you negotiate better.
The mortgage has to be paid off before the escrow can close, and to be paid off, you need the payoff amount. The title company should not have closed, they should have extended the escrow period. However, you should have received the sales funds from the buyer. Just pay off the mortgage yourself when you received the payoff amount and they should file the release of lien. It should all work out fine.
I use 1% of the purchase as a rule of thumb for closing costs excluding commissions.
A revocation of a contractual offer must be received to be effective (see the so-called "Mailbox Rule"), so I would argue that the Notice to Vacate was not legally valid at the time you signed the contractual renewal. However, as the owner has now ratified the contract, the issue is moot.
An advertisement is not a contractual offer and is not enforceable by law in your situation. Your only recourse is to negotiate something in the actual purchase transaction.
The full eviction process takes weeks, so he can start, but not finish the eviction process against you in a matter of days. You will be able to keep physical possession until the eviction process is complete. However, since your lease has terminated on the expiration of the 30 day notice, you are in unlawful detainer, basically a trespasser, which may allow him to collect damages against you. Consult with a local real estate attorney.
Intermittent leaks and floods are difficult to detect. A leaky roof would have visible damage. I doubt you could prove your case in court. Plus the statute of limitations for fraud in most states is 3 years, which you may be passed. Consult with a local real estate attorney.