Making a 24/7 server NEED HELP!?!?!?

so i am running a server onmy home router now and it is realy good but my ip4 adress keeps changing so i need to port forward different ports everyday so i want to make a 24/7 server but i need to know a good hosting site and how manny MB or RAM i need i want about 15 people on the server so i need to know what host is the best and how manny memory i need to buy PLZ HELP ME