Ensure adequate preparation time allowing to practice sufficient number of rehearsals. Last minute engagements have the potential to be sloppy due to insufficient preparation time so be realistic about taking on a project and charge accordingly.
Incorporate any travel, parking and waiting/warm up time into fee.
Ensure all terms of the job are in writing specifically performance date/time/venue cost of rehearsals, cost of performance, number of suggested rehearsals as well as the listof repertoire required.
It may be useful to consider your preparation time when setting your fee-- for example, if you have played the work/s, etc.
Base the number of rehearsals upon the candidate soloist’s requirements. If they are prepared you should not require as much rehearsal time.
Remember your role as a supportive musician. You may be expected to give musical advice to your soloist so ensure you have a clear understanding and knowledge of the relationship between your part and their part so that you are able to advise accordingly, should this be required.
Inexperienced players often require extra support and reassurance with nerves. Be confident enough to provide those as well as your musicianship.