A few random thoughts of my own opinion... take from it what you like, and ignore what you don't.
I think it depends on how wide you expect your distribution to be. Things can always go viral, but if that happens and you weren't expecting it, your audience will think its extra cool that your first release was low budget.
If I were releasing something right now, I, as an individual, with no touring schedule (or any intention of having one), would self-master using my DAW and Izotope Ozone. I would arrange distribution through CD Baby. If I were uncomfortable mastering myself, I would have no hesitation in hiring someone else to do it. I'd look for someone with a proven record of success - either locally with good released products, or over the internet, with a good demo of successful projects.
Understand that mastering is just the sheen and that a good mix is vital to a successful master...
I've been disappointed with several masters in the past, and they were from reputable mastering engineers, not just local hacks.
There are disadvantages to mastering yourself, but if you can remove yourself enough from the composing, performing, recording and mixing processes, there are also advantages - you can re-visit your mix if things don't work out to plan first time around. You also have more control over the final product.
If you are doing it yourself, make sure you have plenty of high quality reference material that you know well, in a similar genre, to compare results.