by far the cheapest and easiest option would be to get a large sledge hammer head and set into a stand of some kind. - I think many people use a bucket of concrete but a decent log with a hollow for half the head would be better (face up)
- I know of a few good blade smiths who started out this way.
another option is to use a section of RR track - this makes a damn good little anvil! - I have a 10" section up at uni with me for my portable forge. - I use mine length ways as opposed to end on like many people suggest to do - but I can do almost anything I want to on it. - I know an old smith who used to swear by it.
viable options are also to use a fork lift truk tine or a section of I beam, these work but aren't fantastic.
do you have a scrap yard near you? - they should have something you could use!
What do you plan on forging? - if it is just knives then a sledge hammer head will do fine!
all the best
Andy