what these guys forgot to mention is good sample cd's. Its almost essintial to have some good sample cd's. I got like 10 of them, over 20,000 samples. If you dont want to create everything from scratch, then you might want some drum loops and bass lines. Thos seem to be the hot stuff in the industry now. I dont personaly use a midi keyboard cause i got plenty of soft synths. Even though some synts can do much btter than softs. If your plannen on doing any vocal recording your gonna needa spend some cheese. if ya got 4 grand, i agree, get yourself some hardware man. You can get software for free off the net, or from your boys. Get a mpc-2000, about $1000, get some studio monitors, i hurd the KRK V88 are really good, but not to sure the price, you might wanna get yourself a power amp to, unless you got something you can use. Get a mixer, a macki would be best.... but.. high doller. If you do decide to get a keyboard and you want something super fukcing nice i would recomend the novation super noca 2 synth with the rack, but retail price on botch can be well over 5000, the synth alone is about 3000, but i think in samash you can get it cheaper.
Anyways with 4000 you can get a tight setup with some good hardware for what your plannen on doing. Dont go and spend 4 grand on software im tellen you.