To a beginner really two things take primacy. Playability and tunability. There are sellers on ebay EK selling new guitars from £25 ($50) plus despatch but of course one has no idea of the playability. Some of the thrift shops here are selling far east guitars for £50 that are playable (so long as you pick the right one) and sound tolerable down the bottom end of the fingerboard.

I would however say go steel string at once. Switching from nylon to steel later is an unnecessary hurdle to create. I would also say to go dreadnought at once. If you get used to a big-body then later when the sound does become important you can get a smaller one if you want and the transition will be painless. But if you have learnt on a parlour guitar and want the big boom it will be hard to switch up several sizes.