Um, lets revisit what mike said...
The rule of thumb is 10g/angel (29 is commonly used for a breeding pair). Loaches are pretty darn slow growers, I've had my 1.5" clown for just about 6 months, and I haven't noticed much growth (nice decrease in snail population though). I'd be more worried about the angel outgrowing the 10g in short order (they get pretty cramped, especially if they're a veil or super veil).
As for buying loaches, about all I can tell you is get ones that look decent (darker black is better). Make sure to QT them, as they will probably get ich due to the stress of the move. Cure with salt (slowly raise level up to around 2tbsp/gal) and higher temps (86), make sure you're doing very regular water changes (daily or twice daily is prefered) while the loach is recovering.
don't know about my water yet because i don't have a tesst kit as of right now
I'm assuming you mean ph and hardness... Do yourself a favor, don't bother with those kits... Make sure your water conditions (ammonia, nitrite, nitrate) are good. pH and hardness are pretty irrelevant unless you're breeding. Never mind the fact that the fish you have chosen are from radically opposite ends of the water spectrum.
I personally wouldn't do it in a 10g, a 20-29 would be better, keeping in mind the loaches would need to be moved in time.