As far as future AP/DLP's go, Georgi Milanov (20, Bulgaria) from FC Litex Lovech is a great cheap option. Don't remember if he gets a work permit right away, but since you're loaning him out it should be all good. Bought him in a few of my games and he's been a steal each time. Should be available for between 250k-750k, depending on how quick you move. His starting stats are already pretty solid, and he's got a lot of room for growth as well. If you're gonna use him as a DLP you might need to coach up a few of his defensive stats a bit, but he's a great prospect, imo.
Also look at Eyal Golasa (Israel... is one of my favorite prospects, though a bit injury prone), Marcus Henrickson (Norway), and Thomas Drage (Norway... more of an AP or CAM/W type than a DLP, imo).
GK's... If you want young English keepers with the potential to one day be a #1, try Jack Butland (Birmingham City), Alex Smithies (Huddersfield), Ben Amos (Man United), or Jason Steele (Middlesbrough). Smithies and Amos have been great investments for me whenever I've managed in England. Never tried the other two, but Butland I know has Wonderkid potential long term if that's what you're looking for.
Hope that helped.