Not much time here, so just a couple of answers.
Bonding is cheap, just call your insurance agent.
Start a wholesale company to buy your cleaning supplies and tools and then sell those items to your janitorial service. Totally legal, and you'll save 40-50%.
A 44-gallon trashcan with casters, a decent vacuum with a hose attachment such as the CarpetPro, a set of restroom cleaning equipment, a dustmop, a mop bucket and wringer, and the small stuff like rags, feather dusters, spray bottles, sponges, gloves. This should not cost over $500.
You can also try Craigslist for good used equipment, and only buy equipment as you need it.
For floors, you will need a floor machine, a wet vac, and probably a buffer. Other items are 2 mop buckets, 2 wringers, 2 mops and handles, some hand-scrub pads for cleaning tight spots and corners, a wax applicator mop, and a couple of box fans. The good thing is that floor machines can be rented at first, and the other stuff will last pretty much forever. Try Craigslist for floor equipment.
People who have been bidding for a while will use both square footage and time estimates. As you get experience you will come to learn how long a square foot takes to clean, how many square feet you can clean in an hour, how the population of a building affects your productivity & time, and even how to figure out a "per-person" charge (if there are 100 people in one of your buildings and it takes you 4 hours (240 minutes) to clean the building, your per-person time is 2.4 minutes - this is a number you can use in your future bids as a benchmark.).
Sorry, that's all for now, but this should get you started on the process.
JanQuest Business Systems
Start Your Own Commercial Janitorial Office-Cleaning Business the Right Way!