Basically this. unless it's through a middleman, or agent etc that are outsourcing it to you, then in general clients really have very little idea of what's involved, thus have completely unrealistic expectations time wise, and money wise, i had a guy basically straight up insult me when i gave him a quote of minimum 8 hours, to model this portable ventilator model properly, clean quad based mesh, he also wanted it on his desk by monday morning, (he contacted me late friday night) i offered to do it for 6 as the lowest as a favour, he then told me he got another quote for 3 hours and i was basically taking the pisss, after i told him it was near on impossible to model that thing properly in 3 hours, you can guess what probably happened come that monday morning when he received the model. Also a lot of people out there wanting something for nothing. luckily a client i've been working with quite a lot lately is literally a dream to work with, then again, he's outsourcing it to me, but i always get detailed well written and laid out briefs and feedback, and prompt payment, he's always offered to pay some upfront and pays extra for revisions etc, but unfortunately these are far and few between