buy the best you can afford, but don't borrow the rent money to do it. The more common newbie rigs like c-4's, 391's, c-1000's, ua-5, jb3, d-8 and the like, can be had for a reasonable price used and when you go to sell you won't take a very big hit and you'll sell quick to the next guy on the fence. That being said, you can buy smart on the higher end stuff the same way. Many times people will sell a complete rig or most of a rig and that is often a great way to buy. Any of the more common posters here will always offer help after the sale also... part of the pleasure of buying and selling "within the family".
Matt