And, getting started is like any business a matter of first putting together your business plan. The business plan is more important for the process of writing it as it makes you do the research and the understanding of what you will sell and who wants to buy it.
As for marketing this type of service, it's pretty much the same across the board. Define your target, will you focus on food, services, brands etc.
Then, define your offer, what will attract them to do business with you rather than a competitor or someone they are already using.
Then, the copy, or the marketing piece comes third, will it be a letter, a telemarketing script and what will it say.
Overall, be sure to plan a new business, it's more important what ou do before you start than when you've started.