stray cat with ear mites

Question
We have recently had a stray cat (I think abandoned) show up at our house.  He is as nice as can be, and my husband consented to let him stay as long as I don't sink a bunch of money into him.  He has obvious ear mites, and I used the over the counter medicine for about 2 weeks.  It cleared the mites in the top half of his ears pretty well, but I still see alot of junk down in his ears.  Is there a natural way to get rid of the mites, or can I keep using the over the counter stuff?  Also, does this put him at risk for any other problems?

Thank you very much!

Answer
Mites chew their way through the skin of the ear canal as a food source, so they do lots of damage.  They can even chew through the eardrum.  So a good ear cleaning by a vet is recommended.  Over the counter ear mite medications do not kill mites that may be on the cat's skin.