Good advice from those above.
I'd just add to that two things...
1- having been to Mandolin Brothers in Staten Island, I can tell you that you will not find a wide variety of OMs there. They usually have a Weber Sage or two, and maybe a Mid-Mo. I don't think I've seen any other octaves or zouks there over 1/2 doz visits over the last few years.
2- That said, the Weber Sages are in your price range also. I haven't played a Peterson, so I can't comment on the comparison, but the Sages are probably in a similar ballpark and are also readily available (and I know someone who may be looking to sell one used as well). IMHO, Weber instruments tend to be a bit overpriced new.
welcome aboard, Dave... or perhaps in your case we should say welcome aground!
Otter OM #1
Brian Dean OM #32
Old Wave Mandola #372
Phoenix Neoclassical #256
If you're gonna walk on thin ice, you might as well dance!