Some people will say small cargo outfits aren't safe because the airplanes aren't pretty. Just make sure your employer does what is necessary to keep the airplanes mechanically sound. Don't accept any pressure to fly an airplane you aren't comfortable with.
It sounds easier than it actually is. Just do your best to stick to your guns if you aren't happy with a mechanical issue.
Flying single pilot cargo in a C-310, BE-58, or other airplane is a good way to build time and experience. I did it in a Baron, and had a great time.
While I worked for American Eagle, I flew with several FO's who had come from flying single pilot in piston twins. They were much better to fly with than some other pilots. You could tell the experience helped them.
Good luck, and have fun!!
