Unfortunately production trumps composition by about 1000% here (and everywhere else these days), everything needs to sound fantastic. That being said, there are plenty of decent sounds to be had for free, check out this old thread.
But yes, with orchestral music especially you will likely have to purchase some expensive sample libraries. If you are really serious though, you might consider trying something like East/West composer cloud, $29.99 a month and you get access to the gold level of all their libraries.
http://www.soundsonline.com/composercloud
But even with something like that you’d still need 4 sales a month just to break even, and you really need a good computer these days with lots of ram to make orchestral mock-ups that sound great, because most of these libraries are ram and cpu hogs.
Otherwise maybe think about getting a part time job, music often requires a large financial investment and many times you don’t get it back. Or, maybe focus on making electronic music, lot’s of synthesizers that can be had out there for free or cheap, free 808 samples, ect, and with a little bit of synthesizer/production knowledge, this stuff can be made to sound great.