Or perhaps someone could make you a set of decals on a transfer car and you could just do the "peel and Stick" on your weekly ride...?
5K a wk is hardly worth it to anyone, you can make more than that in a few minutes on track or in putting anything up on the storefront.
Might be better to ask someone to do a basic livery, pay them well and have them make it in parts that you can quickly adapt to any of your weekly cars.
As far as liveries and sponsors go, what exactly are you looking for..? Simple, complex, colors, patterns, fonts, numbers, logos...?
My wheel bit the dust recently, so I have some time awaiting a replacement. I can't say I wouldn't mind doing an original set up for you to use, but I wouldn't be able to update it every week, and you give very little to go on.
If you'd care to pursue it, the Box Live gamer tag is the same as here, send me an FR. I've got some pics of work from both my own and past auction cars I can put up on the storefront to check out to see if you like th style or work.
Here's the latest project I just finished and a racer just for thought:
You can also pop in the storefront and see 12 other cars for more of an idea.
How much you want to make the design your own will change the cost. Exclusivity being $$ vs me being able to sell similar style (but never the same) being less $$.
Doc