Your grocery budget will obviously get a bit higher - but i wouldn't think by much???
DH used to buy lunches out every day before we moved in together. Now that I'm here and doing the sahm thing I make lunches. SOMETIMES it's leftovers, but usually it consists of:
Sandwich (whatever lunchmeat is on sale, cheese, lettuce, tomatoes,mustard,mayo,bread).
Treat (couple cookies, brownie, granola bar, etc - sometimes homemade, usually not).
I probably spend hmmmm...maybe $20 for 2 weeks on his lunches? Probably less, actually. But even then, it's only $2 a day and a lot healthier than a big mac and fries on sale at mc d's