There are dozen websites which work on the same concept and not to be afraid of anything.
And for your question:
"If I form an LLC for this message board, can I buy a new PC as a business expense? " --- Yes you can buy anything as well run a profit oriented business with LLC. And you can play very safe here. Make sure you use your company account for everything for income tax related queries as well to save couple of bucks if you earn any money.
Here are few suggestions/opinions for you considering you are in Real Estate.
1. Reduce the speed of the flash animation and good not to have sound. If you like sound go for a soothing one.
2.The website doesnt resize the same in all resolutions. Try widening the content area. This will help you to add more information and look better.
3.Lighter the better. Uniformity lacks in the website.
Other wise your site looks good. Hope this information helps.
Spending few bucks can make your website great. Good Luck.