This is dependent upon the industry your business is involved in. If you're an exotic lumber import export business, I would say learning html and css would not be a good use of your time. However, if you are in a company that does 90% of business through developing websites and web properties, then taking time to at least learn the framework of html and css would imo be a good use of time.

Anything is possible, never forget that. To your specific question: Obviously the most critical time a business needs your hands on attention is in its infancy, so being there is ideal, not being there, is not ideal. However, if you have already proven the business in other areas and you have a blue print that someone else on the ground can follow to the "t" that you trust, it could work. Just understand the risk / reward associated with this decision.

It depends on your business, the amount of design work you need done, and importance of deadlines involved In order to keep this answer simple, if you have tight deadlines and at least 6 hours of design work estimated per day for the foreseeable future, the answer is hire in-house, if not, outsource.

The answer to that question really hinges on what the niche of the social network is. Let's say the niche is a about insects. Perhaps an alternative to advertising, would be to send out free bug spray to all members with a dominant bug spray company sponsoring the giveaway of their product. Another example of a way to monetize a network without advertising is to ask for donations once every few months via an email broadcast and banners on your site for a limited time to promote the donation. There are a million ways to monetize any website, it all comes down to identifying your audience and what state of mind they are in while navigating your webpage.