Alot of people will disagree with me on this but I had a reef tenk when I first started and was in the same situation low on cash and I used quick crete play sand from wally world or some where and it did just fine. I had to move about a year and a half after it was set up and everything did great. But after the move I did buy live sand though. but just because the play sand was brownish and I loke the white better now. But if you really get into reef keepimg then you will ALWAYS be short on cash. But as for the sand it really depends on you.
Dave