Before you give an estimate of time and cost, there are two items you should be careful about – Detailed requirements and warranty.
Clear and Detailed Requirements
Many clients think, "Programmers are magicians” and understands exactly what they have in mind. They will send you a piece of paper or bunch of points in an email and will ask you, how much it would cost to get it done. Don’t get fooled with this. First, ask the client to send a detailed requirement of the work explaining every little detail.
Let’s say, a project is a Windows Forms, requires SQL Server as a backend database. Here are some of the questions to ask.
a. How many screens the application will have and details of screens.
b. How many users will be using the application?
c. Where will be the database server residing?
d. Does application needs logging and error handling features?
e. Does application needs notifications capability?
f. Who will be responsible for installation and deployment on production server?
g. Does client has capability to understand the functionality and test the application in production environment?
Make sure all of the answers are written on a requirements document. Don’t take words or emails for granted.
After the requirements are completed, get a signed copy of the contract from the client clearly explaining that this is the work you will be responsible for. If there are any changes or additions, the cost and time will be recalculated and contract will be renegotiated.
Warranty of Code
Don’t give a lifetime warranty. Give 30 days (more time depending on the size of the project) for testing and ask client to come back with any bugs and problems within the specified period. Clearly mention in the contact, after that you are not responsible for any thing happens unless he is ready to pay you extra for your time.
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