Financial aid is pretty generous at HDS. Most MTS students go into Academia eventually, though some choose to get out while they still can or wait a few years before applying. If you do not receive a stipend (there are only a few students who do), then you will have to take out loans or otherwise procure other forms of financial solvency. Heck, even with a stipend, you'll probably need to take out loans. In terms of applying for a PhD/ThD, make sure you do well in your first year, and that you develop some semblance of a professional relationship with a few of your professors. It's actually pretty tricky, I think, since on the one hand these professors will be writing your recommendations, but on the other hand, it does not mean that they will simply let you in. Ultimately, just do well and earn respect that way, and if nothing goes the way you want it, consider it a blessing in disguise! (Since grad school isn't, how do you put it, exactly the most lucrative or stable career to consider)