Don't be put off too much by the adverts asking for 500 hours minimum. When did you last see an ad in flight from a TP or jet operator asking for people with 1000 hours single-engine piston? Yet they're still getting jobs.
The fact is, if companies are prepared to take a chance on low hours or ex-instructor types, or indeed people with SSTRs, they don't need to spend money on ads; they're getting 100 CVs a day as it is.