[Pro Garden Lawn Care]

My business is primarily in the weed control/fertilizing arena, but this spring I'll be doing some overseeding for patchy lawns. I just wanted to ask advice regarding mulching. I will be mowing and power raking the lawn prior to seeding, after seeding is putting down a layer of mulch absolutely necessary? Secondly, would the mulched grass clippings (if I get a mulching mower) do the job? So far the mulch seems to be the most expensive aspect of overseeding. Lastly, what should I expect to pay for seed? Thanks in advance for any advice.