Before you buy it, find out if the lack of permit is something that can be legalized. Sometimes it is just a matter of submitting the blue prints and going through the permitting process. Of course you will probably have to pay any penalties that remain unpaid. Ask if you could negotiate to reduce.
Then decide if it is still worth the trouble and expense.
Best of Luck,
The smoke detectors are easy enough to comply. The basement work could be a lot of money. Is it misc work or an illegal conversion? If the basement was converted to a non-compliant dwelling unit without permits, costs to resolve issues could be $10K+
You can give me a call if you'd like or check out our website. I can review the violation list.