Measure Ghetto by looking at the distance to the nearest predatory loan agency aka Payday or title loans.
Drug test the vents. If you do and get a positive for marajuana, it really scares the sellers.
Look at the roof for shiners. Shiners are exposed nails that should be properly repaired (not covered with caulk that will last maybe 2 years.)
The proper repair is to replace the damaged shingle and anchor (nail) under a undamaged shingle. Shingles have a warrantee of ~15 years when installed like this. Silicon or tar daubs do not have any warrantee, and probably last 1-3 years.
In your case, I think that you may want to buy some spare shingles and take one and cut it to be able to be anchored under the undamaged shingles above the vent and cover the vent pipe nails while having room for the vent pipe. Sorry I can't be more help without pictures.
Edit: I went on a tangent below:
There are a couple spots (like when the roof starts from a wall) where there should be undamaged flashing from the wall that covers the first set of nails.
A quick and dirty trick is to cover the shiner with black silicon and then sprinkle the shingle grit that collects in the gutters on the silicon (so it doesn't decay in the sun, and the repair looks like the rest of the roof).
A less quick and dirtier, but longer lasting fix is to get some roofer fabric and roofer cement, and anchor the fabric under an undamaged single then spread the cement below and above the fabric. It doesn't look great but it will stop leaks from much larger roof cracks (damaged nail base) for a couple years.
Source: YouTube and buying a brand new build house with a bunch of cracked clear silicon repairs to shiners within the first 2 years.
There is a "field test kit" briefcase thing that has swabs that if I remember correctly are paper with a little adhesive. After wiping around in the vent (behind the grate) you can lay it on a paper towel and spray with the field test kit spray. In less than 10 mins it will change colors according to the present drugs on the swab that the spray is rated for.
Well, I didn't want a meth lab requiring me to replace all the drywall. Having the seller get scared when their sweet tenant left marijuana residue everywhere was a side effect that allowed better negotiation. Shrug, I was just doing due diligence, and the seller (via the tenant) left a few things I didn't actually realize were problems until later: a section of uninsulated attic that was unclear without actually crawling in it (my inspector didn't do it), a 240 volt oven whose breaker melted and was only supplying 106 volts, and dog pee infested 2nd story subfloor needing carpet to be ripped up and the floor sealed with paint. Also within 1 year of purchase I had both the shower tub crack and leak into the walls which was both an insurance call and a "restoration company" call, and not 6 months later, a sewer pipe for a sink broke inside the wall. I then said let's sell this place. So shrug, negotiations only go as far as the info you know.