Need help assessing FICO score and new tenant

[Eric Littlepage]

I've taken over managing my C-class duplex for the first time after the last tenant trashed the place, was evicted, and my property management company seemed to be trying to do the least work for as much as I'd keep paying them.  So I've fixed it up, put a bunch more money into it, and am finally screening tenants.  I have requirements of 650+ credit score, income =3.5X rent, no smokers, and while I've gotten tons of interest, I haven't found the perfect tenant yet.  But I'm kind of on the fence about one--she's young, and just barely missed the 3.5X rent requirement, but would meet it with her brother's income, who would be moving in with her.  Her FICO score is 718, which is great, but she has no prior rental history.  So I'm trying to figure out what the FICO score really takes into account.  Would it be a lot easier to get a good score if you just have a couple of utilities in your name and aren't really living on your own yet? 

I've just reduced the rent I'm asking hoping maybe it will draw the better quality tenants, but so far I don't see any difference.