What I will sometimes do in this situation is a free look at the requirements, throw some rough time estimates against it. Maybe even offer to try and manage it

What I will sometimes do in this situation is a free look at the requirements, throw some rough time estimates against it. Maybe even offer to try and manage it for them a bit via some cheaper Upwork developers if they don't like my rates. Of course emphasising that you generally get what you pay for in terms of quality. That's the favour. Generally though I totally agree, i got over working for free after starting a (basically) clone of Uber for a friend who 'just needed something throwing together' when I was 19!