When deciding how to spend your money when it comes to advertising, I believe the best bang for your buck is a mobile billboard. A vehicle wrapped in your company logo, advertising your business's services can be parked anywhere in high visible areas where the public can view and see the vehicle.
The best part about a vehicle wrap is that you don't have to pay for rental space to place the graphics if you own the vehicle. The wrap itself can last up to 10 years if taken care of properly. If you use it on a regular basis then people all around your service area will see it and remember you when the time comes to need your services. This is why city bus's are constantly wrapping their transportation service bus's and renting out the space. It is proven that vehicle wraps are highly effective.
Renting a sign to be located in one spot isn't a bad idea either, but a vehicle can go anywhere and be seen everywhere by any new potential customer. Most businesses have atleast decals on the fleet vehicles and are all branded the same. They all have the same information laid out on them with the same colors, same font and they are all usually the same make and model. But, a full wrap gives that wow factor that no one can compare to. Just make sure that the vehicle wrap you choose that you are 100% satisfied with the design before you get it installed. It isn't like decals where you can just peel parts off to change out some text, you actually have to peel out most of the vehicle to make changes - if not all of the vehicle. If a full wrap is to costly you can always consider half wraps or quarter wraps as well. The first step would be to talk to a graphic designer and see if they have any suggestions or ideas they can assist you with.
A good graphic designer will give you a wrap without re-using graphics that someone else already has, they will spend the time with you to discuss options for layout or give you a visual proof that will allow you to see what it would look like placed out on your vehicle. Don't worry about hurting their feelings by requesting changes either, after all... it's your vehicle.. it's your business and it's your mobile billboard!