If you are not their employee.....  

Depending on what part of the country you are in and how much managing you will be asked to do vs what will be delegated to others plays a factor.  You didnt mention it but is this a 91 or 135 arrangement? How much are they paying you in hangar rent?  Need a few more details but if you are in a major city and part 135 and you factor in your experience and what you think your time is worth then 150K.  If 91, more casual, and more rural area then closer to 100-115k.  A lot of this comes down to you and what you think your time is worth, are you hurting for money or is it not a factor at this point in your career.  Also the pain in but factor, does this seem like its going to be a headache and put in alot of time and effort or will this be a smooth running operation that you just need to guide along the rails.  Its only 1 aircraft but I've seen guys who manage 3 aircraft well over 200k but are also run the entire operation part 91.