Hello iceberg,
We do not recommend bottom of the line VPS for Centova Cast, simply because it's natural that hosting providers would need to cram a hole lot of them per physical server, in order to get back any kind of return on investment. This practice usually leads to overcrowding, which in turn leads to under-spec performance and other irregularities.
If you really can't afford anything more expensive than $4/month, and you can overlook the ocasional hiccup, and you are not planning on serving more than say 50 to 100 listeners, then you will probably be fine with that option, however, if you were to look around a little more for a better option, you could probably find something in the middle like a 1GB RAM VPS for roughly $10/Month.
HTH