If you are just v-carving soft woods or MDF you will probably get away with using something like a palm router as your spindle.

http://www.ebay.co.uk/itm/101748-6MM...item41990493c6

Brand new £43 delivered, if that helps the budget a bit.
If not, keep an eye on ebay/craigslist etc for a small secondhand plunge router you can probably get one for under a tenner.