If he comes to my home country and we get married, will I be issued an immigrant visa once I apply?

Generally there are two options under your circumstances: your U.S. citizen fiance could apply for you to receive a fiance visa for the purpose of entering the U.S. and becoming married within the required period of time, and then applying for adjustment of status to become a U.S. Lawful Permanent Resident (to get a "Green Card"), or you may marry abroad and go through the consular processing steps in the "Immediate Relative" visa category. It would not be an option for you to travel to the U.S. with a visitor's visa while having an intention to become married and apply for adjustment of status, and that approach could be deemed to constitute visa fraud, with the risk of very harsh consequences. Each option has its pros and cons. There really is no substitute for you and your fiance to consult with an immigration attorney who, after learning all of the relevant information, could advise about eligibilities, options and strategies to attain your goals, and who then could offer legal representation in the often complex application process.