Just a quick note about FAA and EASA commercial checkride.
According to the EASA rules the aircraft for a commercial pilot checkride must have at least 4 seats (including pilot), retractable gear and variable-pitch propeller (“complex airplane” in the FAA terms). That is stated in the Part-FCL Regulation (EC) 1178/2011, Appendix 4, Part B, paragraph 1. It can be single-engine or multi-engine (if the applicant already have a multi-engine rating).
Our school uses nice Cessna 172RG with steam gauges.
FAA allows to fly the checkride in any single-engine airplane (for example, I flew in a Cessna 172P). Of course, it’s also possible to use a complex airplane, but it does not make sense - they add additional workload in a stressful checkride environment, and they are more expensive.