Hiring someone to spray my lawn

I am thinking the best thing I can do to improve my lawn would be to hire someone to spray for weeds / fertilize. My grass will start out ok then as summer goes on the weeds take over. I have found the hose end spray type things do work to kill the weeds but it's a big pain to use them. I have also tried the granulated type stuff and that does absolutely nothing.

Can you guys give me an idea of what it costs to have this done? Should it be done multiple times a year? I know I will need to call around but I am trying to get an idea to see if I even want to bother calling around

You can control some of those summer weeds by mowing high and watering a lot. I would call your local spray companies and do some price checking and ask multiple places what they think as your lawn differs from everyone else's make sure you get a few opinions from them and go from there