I get my horse trimmed on all 4 feet and front shoes every six weeks (no longer than 8). I pay the farrier $75 dollars each visit. My vet charges nothing for phone calls. If I have my vet out for a non-emergency, during their regular buisness hours, then it is $30 for the visit (that is just for them showing up), plus the cost of whatever they do. It costs me a little over a hundred dollars to get his west nile, rabies, tetanus and to have the blood drawn for the coggins (which you will need if you plan on riding away from home. My vet also recommends a six month west nile which will be around $50. Now if you have an emergency and have to have the vet out, the cost will go way up.
I think $3000-$4000 is good emergency fund and with $2000 you can get yourself some decent tack.
As for the cost of the horse, this is a buyers market. You should be able to get a good, safe horse with $2000. As someone else mentioned though, it will depend on what you want to do with your horse. If you are just wanting a nice quiet trail horse, I wouldn't go over $2000.
You mentioned buying a horse that's kind of older....about how old are you talking about? If you are planning on buying a senior horse, you may have to have a bigger monthly budget planned out.