I'll propbably have to soundproof the room at least a bit to prevent unwanted reverb right?
A little. If the room sounds good to your ears, you should be able to get a good recording, but good mics do tend to accentuate the reverb a bit. Nothing a few heavy blankets, duvets and soft furnishings wouldn't cure though.
Are those condenser mics very expensive?
Depends on what you buy! You can get a
matched pair of Rode NT5 mics for R3,500 or Oktava MC012s for about R2K ea. You could also get something more upmarket like Neumann KM184s for about R20K for a pair, but honestly, the Rodes or the Oktavas get you 95% of the way there.
A pair of small diaphragm mics are great for acoustic instruments and drum overheads. Add a pair of those to a decent large diaphragm condenser like a Rode NT1-A or AKG C1000 (for vocals and acoustic instruments), an AKG D112 or two (bass & kick drum) and a few Shure SM57s (guitar amps, drums and just about everything else) and you have a full house of decent quality mics that can handle anything you throw at them and you'll probably keep, even if you get other, more expensive mics.
