You got some great advice in this thread as it relates to sound designing for companies that do urban, hip hop, dance, pop, etc., but sounds more like you are asking about random sounds and it's usefulness to be sold to someone. As a person that does both what we are really talking about is two different industries. Everyone does it differently and will surely give you different advice, but I can tell you what I do.
I sound design for companies as a ghost designer. This means that I create sounds that are sold under the companies name and not my brand. Basically I create a package of sounds, I sign over rights to those sounds under a "work for hire" agreement and they cut me a check. As a ghost designer I can typically ask for more money than if I was selling to help promote myself and my brand because they can call the product their own. This method may not work for everyone, but I am a mix engineer first and a sound designer second so this arrangement works quite nicely for my needs. Dollar ranges are about what Cyko told you on buy outs, but it all depends on the project, sounds, etc.
Oh also this doesn't work if you are looking for fame or credit, etc., or if you are going to get mad about the money being made that you are not getting because you sold your sounds away. Early on when I first started to do this I would go to the website that I just sold my sounds to, see the price they were selling it at, then add up all the possible sales they would be getting over time and then be mad....lol. A 14 thousand dollar check sounds good but you take away the taxes (everything over 10k is reported here), pay some bills, you buy a few things for the studio, stuff for the kids and of course the wife wants something, then you get a little something for you and poof that money is gone but they can sell your sounds forever and make way more than 14k...lol..now I just sell and I don't even go to see what they are reselling my sounds for..I just keep it moving.
Now the second thing which is what I think you are really asking about is field sounds (at least I think so..lol) Yes, there are people looking for random sounds for sure! But they are not the same people that are selling drum sounds to folks trying to make hip hop in their bedroom! I sell sound libraries to a lot of independent film companies, business, etc., on a regular basis. See you have to understand that in film (other than dialog) very little of the sound is captured on set. A person walking or kids laughing as an example are all added in during editing. This is where sound libraries come in. You sell them your sound library anywhere from $500 and up (on average I have seen about 2 to 6k). It's not all easy money though. The sound must be clean and clear...not a lot of background noise. You will spend a lot of time cleaning sounds so if you hate that then it won't be fun. Anyway there is more to it is all I am saying. You can't just take a microphone and walk around your city recording stuff. There is an actual art to it believe it or not. Anyway, I wish good luck and much success and I hope all the info you get from this thread points you in the right direction.
