The cheapest that I can think of now, but that will definately add dimension to your club (as I am certain that you dont need dead wood if you got no money to spent):
Vincent Enyeama (GK from H.Tel-Aviv for 220k)
Iliasu Shittu (CB, free agent, plays for Ghana)
Getting a work permit is not a problem and both have age on their side as well. No oldies with no legs! So you can always sell them after a few seasons and make a nice profit. But I dont think you have to, as they are really good.
Plus you'll have some money to spent on some good youngsters. With the money left over look at Mats Rits from Germinal Beerschot (if you have the 3rd patch - 10.2.0) that you can get for 700k - a very good MC prospect, or if you are looking for a striker look at Lacina Traore from CFR Cluj (also the 3rd patch) for 875k. Both have a -9 potential ability in the Data Editor, which puts them in Wonderkid territory. And I am sure that both of them will sign for Stoke. I hope this helps.