Violin isn't the hardest instrument to play, but it can be one of the harder instruments to sound good on - to get a satisfying musical sound, you need to have good 'touch' and control with both hands.
If you have a good musical ear and instinct for the instrument, and can dedicate plenty of time to learning, you could be playing simple tunes within days or even hours. On the other hand, if you are not such a 'natural' (or if you are expecting to sound like an experienced player in a short space of time), progress could seem frustratingly slow.
Is there any way you could borrow an instrument to try out for a while? Failing that, buying second hand can work well - you may be able to sell the instrument without losing too much money if you don't get on with it.
Traditional wooden bodied violins and cellos will always make noise as the body of the instrument amplifies the sound from the strings. To play very quietly, you'd probably need to use an electric instrument (and listen through headphones) - but these are not easy to find and might be a more risky purchase.
Violin prices vary a lot; many cheap instruments come in a set with a bow, but you should check whether this is true for the one your are interested in. You will probably also want to budget for a case and a shoulder rest.
Even if you can't afford lessons, it's always good to get a bit of help from an experienced player just to start you off, check that there's nothing wrong with the instrument you're considering purchasing, and so on.
I've spoken only about violin as I've never played cello. However, from a purely personal point of view, I think the cello could be a more satisfying instrument to play solo due to its deeper register and richer sound.