It's crucial you inspect it properly yourself, rather than say "yeah, so it needs to be this long, straight, free of knots, no twist, no checks, with sealed ends, stored properly...." and expecting a non-bowyer to deliver a suitable log. People try their best to help out, but if they don't have a bowyers eye, you tend to get stuffed up quite easily.
Also, if the log has any character at all, from slight twist to pin clusters and so on (and lets face it - it's wood, so it will!) making your very first bow from it will be HARD. Not impossible - plenty of guys can do it - but tricky. If the goal here is to speed through and get a practical bow, the board route is the most straightforward. If the goal is to learn, make mistakes, develop specific skills and get thoroughly frustrated before having a practical bow, get a log or stave.