I like the idea, but would caution against using anyone you know personally.
This is why. Sooner or later your character will need to say something which your Uncle Bob, Auntie Jan, or best mate simply wouldn't say. A mental conflict is set up and your subconscious won't let the character say it. In the worst possible scenario your character will start to react like the real person as well, instead of how you intended.
This is why spare voices collected in the street and workplace, ('people listening' as well as 'people watching'), can work so well. The actor Peter Sellers collected accents and voices throughout his life and developed characters from the voice outwards. Think about that for a few seconds. It's the sort of thing we writers can so so well. Take one characteristic and build a whole person around it.
Or take one different characteristic from each of several people and build a jigsaw character, but eventually it will be the bits from your own imagination, gluing the parts and smoothing the ill-fitting edges, which turn that character into a person in whom both you and your readers can believe.
Gyppo