I practiced patent law for 9 years until I had my first son, and have been at home with him and his little brother for almsot 5 years now.
You could do a search on your own at the US Patent and Trademark Office's website . . .www.pto.gov. There's a search feature on there . . .you can search patents and patent applications in various ways . . . by title of a patent,by what the patent specification discloses, etc. If you see a patent or application that discloses your invention, then you shouldn't be able to obtain a patent too.
The PTO's website also has a search feature for attorneys in your area. Smaller law firms and solo practictioners will be cheaper than large law firms. And honestly large firms aren't likely to take you on as an individual inventor . . . individual inventors often cause conflicts for law firms who would rather take on companies who can give them lots of business instead of one matter.
If your invention really is patentable and likely to be marketable, I'd recommend finding a good attorney and spending money up front to get a good patent.
The PTO's website also has other information that you may find helpful.
Good luck!