The estimate I got for a pro was $40 per liquid application, 5
applications per year. The liquid contains pre-emerge, fertilizer, and
post-emerge.
If I go DIY I was going to use Fertilome granules with Barricade per-
emerge. Not sure what to use for post-emerge.
Get a good granulated weed and feed like Scotts. Spread it out with a
broadcast spreader. Then spot treat with liquid sprays durring the
season. Don't use Roundup on the lawn, it kills grass. Make sure that
the weed killer you use is the right one for the weed you are trying to
kill. Usually you need one each for Crabgrass and broad leaf.