Don't call other companies, have you neighbor or mother get an estimate from a couple of companies. Also ask your sales leads what did they pay last year.
Vinyl decals are inexpensive. Remember your truck is a traveling billboard (and you don't have to rent the bill board). Take full advantage of it and get signs that are really big. Ask the sign shop about what is best and ask to see some of their work photos for ideas. Signs on the glass are also nice. Tailgate, too. Magnetics are OK--their main advantage is you can take them off when parked in front or a bar. Also magnetic signs are easy to change for the season or special deals or big sales. My magnetic parts of the lettering say "Just say no to" and then depending on the season.."Crabgrass" "Weeds" or " Grubs". Click my name to see my pictures. You could say something about moles, fungus control, seeding, fall cleanup (in fall), Free lawn analysis, first app free, Mother's lawn half price for Mother's Day.
Brochures passed by hand are probably the best marketing method--its tough exhausting work. First week of April is best. Knock on doors if you can. Remember it costs about $80 in advertising to get one sales lead.