There are also ways to increase business without spending additional money on advertising. I think the one thing many people don't think about is using their existing customer base to build their business. I scaled my business down to part time when my wife and I had our daughter due to the high costs of daycare and not wanting to miss her growing up. When I'm ready to go back to fulltime, I plan on asking my existing customer base to refer me to friends or neighbors. I'm pretty confident that most of my customers could probably get me a customer. I would think I could probably almost double the business through them (especially if I work it in with a referral type program). I take good care of my customers. They like my work. I feel my prices are fair, and I help them out from time to time (for a fee of course) with things that aren't neccessarily in the scope of my normal duties (i.e. haul stuff to the dump for them, pick up and deliver big bulky things, etc). Let it be known to your customers you are looking for more work and insure them it's not going to sacrifice the quality of work you currently provide.
I also think you need to network with local contractors who do your quality level of work, not in your field and work to help each other out with referrals. One of my customers is a plumber and has asked me several times if I'm looking for more work but unfortunatetly at this point I'm at my max while still being able to do things wth my daughter. Anytime the topic of plumbing comes up with my customers I push his name.