Don't forget community college continuing education programs or those sponsored by local school systems. Many have sessions on basic marketing. I believe most persons are willing to help as long as you don't take advantage of the situation. Don't expect a full blown marketing plan in your lap. Marketing consultants are an excellent source of help.
Charges can vary from very reasonable to prohibitive.
Rates are usually not an indicator of ability. If you will take the time to do some basic research, you will find that a good marketing plan is affordable and within easy reach of anyone.