I use the Groundskeeper Pro program. It's in the neighborhood of $400 - not bad for all it does.
Billing, customer list & info, track expenses, employee wages, company info, accounts payable, estimates, ect.
I bill at the end of each month, I usually have checks coming in all month because some customers pay quick, some middle of the month, some end of the month.
I'm able to set the specific due date each billing cycle - if I want it changed. - Check it out, you may like it.
13' Chevy 2500HD Duramax
13' JD 661R Quik Trak 61"
11' JD 930A Z 60"
05' JD F1445 Diesel 72"
13' Bobcat T650 CTL
08' Haulmax 24' Enclosed Trailer
11' JD JS 26 W.B.
12' BOSS 9.2 V-XT plow+Wings
Stihl hand held eq.
10' L.W. 13hp blower
13' Permagreen Triumph
WI certified pesticide applicator