As someone mentioned above, try to find someone local to build you one, because they will have a locals perspective and any research they do will be in the area where the business and customers are located. This also allows you to meet face to face with your builder if you need to.
Since you are just starting out, or if funding is tight, do a search online and find a really good template for a real estate website. In particular you want to be able to get a few beautiful homes on the home page with your picture (or an attractive female agent) prominently displayed.
It is critically important that your phone number be prominently displayed and has a contact form on the home page. It must be painfully obvious how to get in touch with you and as simple as possible to accomplish. Give away a free e-book or put a mortgage calculator on the site, or both.
When you find a template you like, run an ad in the paper and ask for a web builder to use the template and modify it for your company. What you should put on the site and SEO are a completely separate discussion. You should expect to have to provide the written content and any images you want on the site along with permission to use those images. You can expect to pay $750 to $1500 for a 10 page website this way.
If funding is not a problem, you should find a local web designer and have them design a custom look and feel for your web site. In this case you are not bound by the look and style of a template or theme, and the designer can design your site to look exactly how you want it to, or create one for you that has the features you like and functionality you need.
After the designer has designed the site, you then take the design to a web developer who will turn the design into a functioning web site.
You can expect to pay $2500 + (mostly +) for that level of service.
Resist the temptation to use a free website builder or build it yourself. Anything less than superb is going to make you look unprofessional and sloppy. When you customer sees your home page the first impression they have should be smiling helpful face(s) beautiful homes, and perfectly written articles.
Have the content edited, or better yet written by a copywriter. Proper grammar is absolutely critical.
Make sure that the person building the website can do "MLS" integration. This is the standard real estate network of available homes, and you need it on your website.
Your real estate site will benefit by having a page dedicated to the better neighborhoods in your area. This page (or better yet, section), should discuss schools, shopping, entertainment, community, etc. This will cause your site to pop up in the search engines when this neighborhood is included in a search term.
If this happens, you might end up with this neighborhood page and your home page on the first page of Google at the same time. <Good Times>