I could be wrong, but for an in country Non-O based on being over 50, the rules do state that the funds come from abroad. How wide that rule is applied? Who knows.
The single entry Non-O based on being over 50 (retirement) is most certainly an option on the e-visa scheme. Also, when in country you would apply for an extension based on being over 50, the Non-OA is only available in your home country and comes with health insurance requirements.