if you have less than a grand, the only good fully your going to be able to get that can handle DH is going to be pretty beat up. my adivice, is dont bother. hardtails are by far, the best kinda bike to get started on.
1. they are simple, less moving parts to wear out, fix, or maintain (full suspension bikes also put extra strain on the drivetrain, they get fucked up more often), you GOTTA keep an eye on pivot bushings/bearings, etc. LOTSA extra maintnence
2. it teaches you proper riding technique, how to flow over obsticals instead of just crashing over them. it also teaches you to spot, pick, and commit to the smoothest (and fastest) lines through the gnar.
3. they are versitile. a good burly hardtail will have no problem slaying DH, hittin Dirtjumps, doing drop offs, some urban, and even XC, since theres no bob in the pedalstroke. this is great when you still havent really figured out what you like to ride and are doin everything. most fullies are pretty terrain-specific.
4. they are just fun. hardtails usually have tighter geometry in the rear end, and it makes them very agile and incredibly fun to whip around singletrack
once you have a season or two under your belt on your hardtail, THEN you get your nice new fully. you will be a FAR better rider, and will really be able to take advantage of the extra preformance, you will be more used to doing the regular maintnence, etc etc. i started off on a POS trek 820, then got a freeride bike. it helped so much. 2 years ago, i swapped out the bike for a hardtail, and its just as capable, and definatly more fun.