Expert services are opaque – outsiders find it hard to see what goes into them. So when a friend asks you for a “quick professional favor”, they actually have no idea just how big that favor is.
Often, they will even sense that what they are asking for is (probably) not trivial, so they offer to pay – which can make things even worse for you.
Should you charge money for favors, and if so, what kind of a discount should you apply?
The problem is, usually, any amount of discount seems out of place – too low and you shouldn’t have bothered, too high and the friend can feel like you are giving them something trivial. Additionally, any revisions, additions, changes, or just plain indecisiveness are very hard to adequately cover during the work without damaging the relationship.
I would argue to keep things simple – either charge them full price like a Client or charge them nothing, like you would treat donating your time to charity.
If the friend is in need, “charity” is usually the obvious option. If it’s more of a “friend” who makes one-sided calls only when they need something or a friend of a friend’s aunt-type situation, treating them like any client that comes from a referral keeps the relationship clean and clear. The latter “clients” may not like it much, but I find that entering into a half-client relationship often does even more damage in the long run. If all else fails, blame your “change of policy” on me:)
Either way, keeping clear of the “soggy ground” between the client and favor territory is a universally good idea for Expert service providers, and will serve you well as a principle.