A mediator does not decide your matter. The parties decide the matter while in mediation. A mediator will use techniques to assist the parties to reach a conclusion to which the parties will agree. While there are different types of mediation and some variations, generally, mediations are conducted confidentially. In the event that the mediation does not result in settlement, you will generally be able to present your case basically as though there had been no mediation.
Generally, the issue of financial wherewithal is considered an issue more of support than of custody. The issue of whether a party has financial means is ordinarily not very probative in and of itself as to the child's best interests. Underlying issues, however, that may cause financial instability, may be very probative to child custody. Substance abuse, emotional instabilities, irresponsibility, etc. are all issues that are very probative in addressing child custody issues.