PRN pay in Houston

[ms.minchin]

I got a job offer for a PRN level 1 position in Houston for $28/hour plus any shift differentials. This position requires you to work at least two shifts every four weeks. It's about $6 less than what I make with my full time job. I have 4 years of experience and certified. Is this the typical rate for PRN in houston? I was under the impression that PRN rate is typically higher than full time rate. I don't know if I should accept or not because I don't really have an idea of the pay scale around houston.