Your best bet if you are thinking about getting into top-spreading would be to skip the bags and get either a truck bed, trailer, or dump trailer full of organic compost.
I did a quick Google search in your area, and here's a link for bulk organic compost at $25.00 a ton (just a quick scan of their website).
Their address is: Silver Creek Road NE in Rochester, MN
This would be your best bang for the buck. Plus shoveling higher than your top dresser machine is easier when your above it. Just pick up a little step stool to step in and out easier.
I can move about 10,000 pounds of compost in 4 to 5 hours. And you should charge about $60 to $100 a ton. This would include organic compost, delivery, spreading, clean up, and the customer buys their seed.
So if the seed doesn't germinate....then it's their problem and not yours. I just direct them to the "Big Box Stores" since they usually have a high turn over rate of material....because with all this work you put into the yard....if the seed is not good....then the customer isn't getting all the benefits of organic compost.
2,000 pounds (1 ton) of compost for $25.00 or 2,000 pounds (1 ton) of bag compost (40 pounds a bag @ $4.00 or higher per bag & tax) would = $200.00 or higher at Big Box Stores.
Go with the local compost and get something to haul it.
2013 Ford F450 Super Duty Truck
2010 Exmark Lazer Z 60" deck
2012 ExMark 30" Riding Aerator
2011 John Deere Pro Gator 2020a
2011 Lawn Solution Dual Hyrdo Aerator 24"
2011 Echo Handheld (trimmers to power pruners)
2007 Big Tex 4ft metal high side 7' x 12' Trailer
2012 PJ 7' x 16' Dump Trailer
2014 Vintage 8.5' x 24' Enclosed Trailer
2012 Ecolawn Applicator model 200 Compost Spreader