Planesense has many pilots that are 55+ and from what I have seen age has nothing to do with the hiring process.
Assuming you get the interview, the main disqualifiers would be weak IR skills, weak Jepp knowledge and a perceived unwillingness to do the dirty work (i.e. cleaning the interior of the plane on empty legs, restocking the catering and emptying the lav if necessary). There is also a heavy emphasis on personality as you will be interacting directly with the owners and playing the role of gate agent/flight attendant/pilot/psychiatrist.
Once getting to training you'll find that the Honeywell Apex has a steep learning curve. Do everything you can to study up on that before hand.
I suspect they will consider applications for FOs at 500 hours if they feel you have a good handle on all of the above.