Any nearby Thrift/Goodwill type stores? You can find some very good desks (and other things) for remarkably low prices.
And, if you have any big box stores that carry desks look for sales on floor models.
Avoid desks made of particle board, especially low end models. Those desks may not hold up well.
There is a lot to be said for a simple slab door across two 2 drawer file cabinets...