Northern Belize is a great place to live modestly and comfortably but not a place to make money and particularly not in tourism.
As Lan, who knows more about tourism and the economics thereof than probably anyone I can think of, states, you will lose a lot of money. There is no money in tourism infrastructure in the Corozal area. There may be opportunities in residential housing development in the area, you should probably have a chat with Bill Wildman. Corozal, Consejo, etc. has good potential for retiree and emigre housing and there is ample land available for that purpose.
On the other hand, you may have a lot of money or you may be looking for a tax shelter or something other than income. Don't want to pry....
As far as the BTB is concerned, if you are at the stage of investing large sums of money in Belize you must already know that the purposes of government agencies in Belize (as in most places) is not to assist the business community but to extract every penny it can from it. There are organizations that can help you in tourism development (such as BTIA for example, the various chambers of commerce, etc.) but it is most imprudent to look to government entities to assist you. The best thing you can hope for from the government is benign neglect (that they leave you alone). Keep your hand firmly on your wallet at all times.
If you are very lucky and plan well, you MAY (in a few years) be able to make enough money from whatever you develop to allow you to live comfortably albeit modestly in Belize but that is the most you can expect. Northern Belize is a very nice place to do that. You may want to visit www.belizenorth.com
for some helpful advice from a long term resident there.