The single best paid and most reliable musician job for most people (I'm excluding the miniscule fraction who actually make it big) is as part of a wedding band. Certainly in the UK you can get at least one gig a week if you play covers, as there is high demand, and the money is definitely enough to live on - can be considerably more than some full time professions such as nursing.
Never ever Pay to Play - it is mostly a con set up to benefit promoters (I know, some exceptions, but if you are new to this sort of thing, assume it will be a challenge figuring out which ones!)
If you are good, research your market and promote yourself.
Marketing and selling songs nowadays is straightforward - you can do the entire thing yourself, and promote through facebook, fandalism etc., sell through iTunes, Amazon, Play etc and even run merchandise through Cafepress...
I am very part time these days on the Music side of things, averaging about one gig a month, and I still make money from it. As we are not a covers band, we don't make a steady income by any means, but festivals pay a decent amount, large venues also pay well, and even pub gigs cover our petrol and beer. Royalties from online sales make us a wee bit each month as well. I would like to make much more, but it's good to have a hobby that makes anything...