most providers won't even talk bgp with you unless you go for a /24 from them. if you're wanting diverse carriers -- some isps require you to have your own allocated space.
good luck with that.
when you recover for the price from your providers/arin/et al -- get back to us.
My experience with low-end round robin load balancing or active-passive failover is poor, which is why I'd like real BGP.
you're doing it wrong.
i've set up several networks with such balancing -- even active/active. the only issue is continuity of business services (vpn, nats, etc). depending on your business requirement for such functions -- the cost for a netblock may be worth it. thats a cost benefit analysis left up to the reader.
"...if I in my north room dance naked, grotesquely before my mirror waving my shirt round my head and singing softly to myself..."