Characters with Item History may hire out their services to other PCs for 25sp per rank. Downtime spent must come from both PCs. Because downtime costs 30s a week this means it is not profitable to sell services to other PCs until you have two or more ranks in something.
NPC sages are available, but charge 50sp per rank. They roll Step 6+Rank, and unlike PCs, will not spend Karma on their attempts.