What is the domain expertise needed to market and sell products in US
in the following sectors i.e. Telecom (e.g. Telecom Serivces),
Petroleum (e.g. Gasoline), Financial Serivices (e.g. Mutual funds,
Bonds, Mortgages) and Consumer Goods (e.g. Soap) ? What are the
similarities and differneces in the domain expertise ?

I believe that to answer it well, your question will require more time
and effort than the average amount of time and effort associated with
this price. Here is a link to guidelines about pricing your question,
in the pricing guide:
https://answers.google.com/answers/pricing.html