If you want to run your own business (as long as you will be paying sales tax to State) you need to register a company with state. There are different catagory. LLC or Inc. Then you will need to register for the permitt with the county where the mall is located. They  require you as a owner to be legal in the country (sometimes you might be lucky enough where they will not ask for your legal status as long as you have your social security number but you might be in trouble at the end of the year when filing for taxes). If investing money with other legal status folks please becareful and invest wisely. Also make sure you talked to mall management, They might not let you open one if the cart in that particular mall already selling your product like you mentioned earlier in the thread.  I know sun glasses are nice and have a good margin. Also those funny t-shirts are good seller. souvenior if you live in tourist spots are good seller as well. Tickers watches with souvenior for the city you live in is also a good idea. Bags occupy a lot of space although you can hang them but might not have that much of a margin. Also your idea of starting a business in January is wise coz rent is way too high for the month of Nov and Dec. You might say its the best season of the year but you might be on tight budget and hard for you to have cash flow to operate a business.

Its just my thought. Love to hear more ideas