It should be no problem you just have to designate which flights are going to be training flights and which ones will be 135. There are some 135 carriers that have an arrow/warrior/bonanza/172 that use it for both purposes. Please note most of these aircraft are limited to VFR ops only for part 135. The FAA aircraft requirements for single engine aircraft in IFR can be quite lengthy. Depending on what type of aircraft you're operating.