To reduce financial burdens, most MD-PhD programs support trainees with a stipend and tuition scholarship during medical school and graduate school training. However, there are variations on the amount or length of time that students are supported. For example, some programs limit the total numbers of years that the stipend and tuition are provided.
Programs may also provide some support for travel to scientific conferences or research expenses. Information on support from specific programs can be found on the program's website or by contacting the program administrator.
Although most MD-PhD programs offer substantial support for their students, there are additional resources available for supporting MD-PhD trainees. Most take the form of competitive applications submitted by the trainee and their research mentor. These include fellowships from private sources and from a number of NIH institutions as F30/31 NRSA pre-doctoral fellowships.
Programs are likely to differ considerably in their expectations of trainees regarding such resources. However, in addition to the possibility that your application might get funded there are other benefits to consider. In particular, by engaging in the process of grant writing you will focus your research project and acquire an important new skill necessary to lead a laboratory.