I've had a few projects on my laptop that have been developed for previous clients. I've been thinking of actually building upon the projects to build bigger projects on my spare time or when the time comes that another client is need of a more complex or less complex software, I can just modify a few things and deploy much faster.
What do you think? Do you do this?
EDIT: The projects were made by me while freelancing.
Who owns the code? This is ideally defined in an SDA between a contractor and the client, and it sounds like you may not have drawn one up for the previous work.
I'm no lawyer, but I would suggest you consult one on this. It could come back to bite you.
As long as the projects belong to you then it is fine and it is a better solution (Why reinvent the wheel). but if you have worked on the projects which belongs to your company then you dont have the right to work on it for another client ;-)
What ever you do in your office premise belongs to your employer. These include simple tools which you develop to make your daily job easier.
But if these projects are your own then there is no harm in doing it. I have many times reused my own projects.
Edit: Now you have said that these projects belong to you the I would encourage you using it as long as you dont have any agreement with the first client.
I have worked on projects in which clients ask us not to reuse the code even though we dont share the code with them.
Warning: I am not a lawyer - take with a grain of salt. All legal advice differs based on your locale.
It completely depends on the contract you had with your first client.
I always try to write contracts in a way that I own all of the rights to the code that I write, but that's not always the case. If you own the full ownership rights to your code, you are welcome to reuse it any way you wish.
If your contract prohibits this, or states something that the previous client "owns" the code in some way, I would avoid it.
You developed the code for some clients but do you own the code or the client own that code. If you own then surely you can use that code to develop further for other clients. But if you don't then you cannot reuse it.