Yes the idea will work. Although to get the right percentages of fert/weed control will be next to imposible with direct injecting from the high side of the line. To do it you would have to premix the chem, in the tank. This will contaminate the poly tank and cause more issues. Look into the insurance licensing and liability plus the seasonal aspect of the lawn spray bis. IMO it is better to specialise in somthing and know it inside and out rather than to dabble in ten different things.

DAFF

DAFF MOBILE WASH
WINDSOR, ONTARIO CANADA
DAFFMOBILEWASH@AOL.COM