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"Get yourself endorsed on something that is likely to be operated on GA charter ops.
Baron, C310, Aztruck, C402, PA31"
I agree but you will need a few hours under your belt to get a C402 or alike gig and to get endorsed and then find there are no jobs on aircraft of that type is an expensive exercise. Best bet is to have your MECIR done then get on the blower and talk/email/write to operators about a job.
More often than not if you meet their requirements and they want you they will either ask you to get an endorsement on a particular aircraft (money well spent) or offer to endorse you (money saved).