Since hip hop and RnB typically use mostly fake instruments, you are probably better off investing in some good samplers. The main mic you want to spend your money on should be a vocal mic.
The u87 is the industry standard, but there are plenty of others that are excellent as well.
You want to pick up an SM57 as well because it works on snare drums, guitar cabinets and just about everything else.
I have the capabilities of miking my cabinets, but for tight rhythm, I love the sound I get from
my Pod XT pro. You can even change the sounds after you record them which is awesome (including the distortion, cabinet types etc)
Those 3 things together would run you about
u87 - ($1700 new)
SM57 ($80 new) ---- $2500
Pod XT pro ($700 new)
For drums I would suggest getting a great kick drum mic such as the d112 or the shure beta (52) They are both about $200
Then all you need are small diaphragm condensors (SDC) mics. You can pick up a pair of Studio Projects C4 for about $320 new. They are awesome and can act as drum overheads, or can mic acoustic guitar in stereo.
Bass guitar and electric acoustic can both go direct into your soundcard, or into the pod. That would cover everything for you.