Janitorial contracts are bid on by writing up a proposal listing the services to be provided, the bidder's janitorial experience and the price the bidder wants to be paid to complete the job. Good proposals include references and competitive bids.
A competitive bid is the key to winning a janitorial contract and still making money. The best bids are lower than the competition and still high enough to make a reasonable profit. Doing research on typical janitorial rates in the job area before setting a bid amount keeps bids on track with the competition. The desired price needs to include enough money to cover supplies, salaries for additional laborers, if necessary, and any business overhead.