Be careful about undercutting your competition.
First of all, it might seem to them to be unfair competition. In and of itself that might not affect you at all, but maybe some day, you're gonna need a favor from someone and this'll come back to bite you.
Also, be aware of what message it sends out, or perhaps more accurately, how others might interpret this. You're so cheap because your reputation is bad and you can't get any work otherwise. You're so cheap because you don't think your time is as valuable as that of a proper lawyer.
No matter what people might think of lawyers in general, there's one thing they'll tend to agree on: the best lawyers get paid the most. Being the cheapest lawyer in town is not a good thing.
Unless you can give another (apparently) valid reason for having such low fees. Some part of the standard 'lawyer' package that you won't be giving people that allows you to have less costs, which you pass on to your clients. Like, I don't know, for example, not having a proper office. Tell people how computers and the net allow you to be more efficient on the road the whole day, so you don't need an office and all the costs it entails. Of course, it also means that they can't send you snail mail, unless it goes to your home and then you won't read it until the evening. But any client who doesn't need to send you anything or who doesn't care about the delays will come to you because you're cheaper.
Give a good reason why you're cheaper, or people will assume the worst possible reason: that you're actually no good.
Oh, and the reason you give doesn't actually have to be true, it just needs to be plausible.