You are perfectly suited to doing this for all kinds of businesses. I do this for a living, only more focused on high end builders and contractors. By setting up your own home office, you become an independent contractor. Ask your boss about the option of keeping that account as an independent contractor, and he will probably jump at it, because it costs them less in taxes, unemployment, benefits. Purchase upgraded computers, software, and start gaining as many clients as you can handle.
To start without a lot of overhead, advertise your business through direct mail postcards, (get 100 free from Vistaprint.com) and going out and getting accounts in person.
The tax advantages of a home based office are great. Plus, working from home has greatly improved our quality of life. My schedule is flexible, and what I make is directly up to me. However, you need to be a self starter, someone who works well without supervision. Have regular office hours, and use a cellphone as your business line, so you are always accessible.
If you are already good at graphic design, have your printing done full color at one of the online printers. Printplace.com or printograph.com are both good sources for everything from brochures to business cards to postcards and folders. In addition, get a working relationship with a couple of local print companies for smaller jobs. Invest in an all in one printer, flatbed scanner, fax, copier, I love my new HP from Staples...just $150 and the cartridges are inexpensive, but the quality is great. For more than 50 pages though, its usually worth heading to a commercial printer to have them copied.
Think of all the other businesses related to real estate, and all the home inspectors, appraisers, builders, etc who you have met in the office. They would be good potential clients, as well as all the other realtors out there.
Get a couple of books from your library on starting a home based business, on graphic design specifically, and have a professional looking office or space to meet with customers in your home. You don't need to spend a lot of money on this, lots of small businesses start out making deals at the dining room table. I started my business three years ago with a computer, desk, and a few good contacts, and learned along the way.
Once you get established, you can become a representative/distributor for list brokers, promotional products, print products, etc. and get a cut on all you sell. One company that has great stuff for realtors is Tradenet Publishing of Kansas. They do full color laminated or magnetic business cards, magnets, calendars, dry erase boards, etc, and that gives you a product to sell. You will have to get a sales tax license, but thats just a form to fill out. Once established with them, Distributor Central is a great one stop place for custom promotional products for resale.
Consult an accountant to get your initial bookkeeping setup, and make sure you have everything filed correctly, and do your own billing with Quickbooks Simple Start.
Best wishes! You will have a fun and rewarding career if you freelance. Scheduling vacations is easy, just don't take on as much work on about a month before, and take your cell and laptop with you so you can stay in touch and not lose on potential jobs.
One word of advice....try to start your business without borrowing any money. Get a couple of paying clients, then buy stuff as you can afford it. That way, if it doesn't turn out to be your idea of a dream job, then you aren't out any money. Using vistaprint for your own marketing materials to get started will help greatly.