Also, fishtape, would be good.
Stud,electric,metal, etc. locater(finder)
Voltage presence tester\sensor
Cable testing units
A very good assortment of handtools
drill motor and various bits(wood, mason, steel, etc.)
Klein splicer scissors and knife
Portable power source (like an onan)
Portable air compressor(great to blow tape thru conduit and flexi-duct)
Ladders
Tool bags
Toner and tone finder
Multimeters (analog and digital)-A Sidekick, instead of analog multi-meter, is a good choice; if you can find one for a deal.
Butt set or Hand set(compatiable with digital circuits)
Turtle
Spin-down tool may be useful in some locations
Punchdown tool
Thin nose needle nose pliers are a must sometimes
Looking into being bonded(insured).
Check on your locality's license requirements.
Check into, whether, you wish to be sole proprietorship, partnership, incorporating, etc.
There is a lot you need and need to know... I don't know how far you plan on carrying the business, but a lot large jobs will want someone to do the whole thing. Like from the demarc on. In that case you would need more test equipment and tools. Also, an understanding of equipment, testing procedures, etc. of the project you will be involved in.
Most of the vendors, I worked with, did the inside from the demarc and all the electronics(loose term).
The only time I remember a vendor doing just cabling\wire, was in a residential setting.
Goodluck in the venture.