The BIG idea !!

My big idea is to build a robot.
There are plenty of toys and gadgets that does exactly this, but I want to build mine and i want it to be like I want. Of course, I do not have the budget of NASA, so it will mostly be made of bits and scavenged parts. Here are some requirements and limitations I have:

- The robot must be able to go outside (garden) as I do not want it to sit in my house and take space for nothing (well, this could be my wife requirement:-) Also, I have a small kid and I do not want him to get his hand of finger stuck in a gear or something.
- This robot must be as cheap as possible
- This robot will not clean the floor or cut the grass, for this, I could buy one already done.
- I hope to make this robot clever At least, be able to navigate by itself and have some interaction.
- This robot should fit in my car, and thru doors (60cm wide max)
- The robot ill run ith VB code (I like coding in VB)

Ok, so now lest start building....