My FNP director told me at the interview that she does not recommend to have a full time job while in FNP school. I am in Indiana, I am working with a instate health staffing agency, they post the long-term care facility shifts that need RN covering, I just pick ones that I am available and willing to do, they pay a lot higher, just no benefits. I like the flexibility of it, I can work any time I want to, perfect for student NP. If you worry about employment gap, this is an option, you still work, just with agency, but how many shifts you work a month, they do not have to know. IF you want to work in hospitals through agency, usually those require a contract which I don't want.
But I don't think the gap matters, because the RN experience doesn't even count much at all when you first apply for FNP position.