I am currently in a Ph.D. program in Human Genetics. A number of programs will let you jump straight in with only a Masters, including mine (U. of Utah), though sometimes it is bes to go for a MS first. It will give you more research experience, help you figure out what you might want to research, or even if that is the right choice for you, plus you can spend 2-3 years on a project and find out it sucks rather than 5+ years. You also get to try different areas of research.
In terms of stipend, molecular biology program tend to pay over 20K (my stipend is at 23k this year) because you will be doing important research for your lab. You will not be rich, but you can still pay your bills and you do not have to go out and get an alternative job (as people in many humanities and social science programs have to do, sometimes even with a stipend b/c it is so low.)