buy an old machine which is a well known brand with as little plastic parts as possible and then when you have more money and you know what you like in a machine after researching then go out and spend but above all take your time! Look at buying used as many people just trade up and the machines are often a good buy. That way you will also have a spare machine if your other one has to go into the shop.
Try all different machines but the features that i couldnt live without is drop feed dogs, needle down everytime it stops and if i ever buy a new machine it will have the biggest throat space imaginable!! Low bobbin sensor would be nice too and i also love the little thread cutter on the side of the machine.
If the machine comes with a walking foot then count yourself lucky as they can cost quite a bit.. all other feet arent that expensive. good luck finding what you need...
:D