New to the group, hope someone can offer help...

In short, I'm a landlady, and I have a tenant living in the basement
of my house. He has an indoor-outdoor cat that he lets out during the
night. I know this isn't a good thing to do, but I can't interfere...
We live in a house, so the tenant has access to the main floor and the
basement (his living quarters).

Two weeks ago I started getting very nasty bites on my feet that were
larger than mosquito bites. When I had just two, I figured it was a
fluke, then I started getting more. My husband has small little red
bites on his feet. I figured at this point the cat probably brought
fleas into the house.

I took the cat to the vet, out of pocket (after finding out which vet
my tenant usually sees). $160 later, I left with a fully vaxed cat
(vaxes were unknown, vet said he hadn't brought the cat in over two
years). And six months of Advantage. The vet applied the first
application to show me how to do it.

So basically I'm taking responsibility for this cat that's not being
very well looked after... and what I don't know how to deal with is
the fleas. The cat has no access to the upstairs because of our
allergies. I have not noticed getting any flea bites upstairs except
in the bathroom (I washed the bathmat, I had bites on my toes and I
always wear socks). My entire floor upstairs and main floor is
linoleum. The tenant doesn't spend much time in our sitting quarters,
but I'm assuming there's a chance fleas came upstairs with him. He
uses the same bathroom where I got my bites.

The basement floor is concrete and uneven, so it's not really easy to
mop it clean. I don't even own a vacuum since I just pay someone to
come in and clean the upstairs and main floor once every few weeks to
take care of dust mites, etc.

This is really bad, because although I only get a couple new bites
every few days, these bites are around 1/2" wide in the swelling, and
the itchy area is around 3-4" wide. I'm reacting really badly, so I
need to know what else to do to get them to go away.

The vet told me that I wouldn't need to fumagate because the cat would
be a vacuum for fleas and they would die on contact, and eventually
they'd all be gone. The cat has no bedding and his makeshift bed
(cat's own choice) is an empty cardboard box that's in my storage
area. That's where he goes to sleep most of the time. I don't see him
sleeping on the furniture when I go down there unless the tenant has
left clean clothes lying around.

We treated this cat with Advantage on the 17th, so that's almost 2
weeks ago. I just got four new nasty bites yesterday, so I know there
are still fleas around. What I don't get, is why they are biting me
instead of attracting themselves to the cat. The tenant is telling me
he has no flea bites or irritation, so I'm not sure why he's not
getting bit of all of us are. I'm also trying to figure out if we're
in fact getting bit on the main floor (since there's no cat up there
for the fleas to bite, I heard they will bite humans if they are
hungry... we found this out the hard way when a cat who had fleas
passed away, my mom got bit for weeks. She spent lots of time
vacuuming to get rid of them, but she didn't use any sprays or
fumagate).

Thanks for your help
Sapphyre (& Jags the cat)