The domaining business, unless the OP is going out of his way to cybersquat, is relative safe compared to the web design business.
I DISAGREE. YOU CAN EVEN GET SUED FOR "COMMON LAW" TMs.
To be clear, my point to the OP is first focus on setting up his web design business separate from everything else.
AGAIN I DISAGREE. THE MAIN POINT IS NOT TO SPLIT YOUR BUSINESSES, THE MAIN POINT IS TO INSULATE YOUR PERSONAL ASSETS.
Putting various types of businesses all in one entity comes with its own risks - and conversely, having a separate entity for every type of business one does can add a lot of complexicity and cost.
YES, UNLESS THEY ARE BIG BUSINESSES, IT MIGHT BE HARD JUSTIFYING A SEPARATE ENTITY FOR EACH BUSINESS.
In regards to my comment about personal ownership / dba for his domains, that may be fine depending on the value / nature of the domains he has, at least for the timebeing.
I DISAGREE. THAT'S HOW YOU GET SUED PERSONALLY.
And finally, potential liability for a web design business can be far more than what the client paid (ie. failure / improper licensing of content, such as stock images), and the liability exposure even moreso, if the services provided include web hosting, programming, and ecommerce (ie. a hosted shopping cart, credit card processing, etc).
NOT IF YOU HAVE A GOOD CONTRACT.
HAL