Personal experience...dont do it....well actually depends which way you look at it.
My situation:
Bought with a football team mate, i always knew the bloke was a tad odd (he said the house would be kept spotless as he had OCD...wrong OCD...he wanted everything organised shoes etc)...but after we bought a 2 bed, i should have seen the signs when he painted a door shut, wanted to paint around his bed and not the whole wall....left the cooker on numerous times and left the house, left the back door wide open and left the house...oh and left the heating on all through the night on a boiling day and wondered why the next day he had woken up so many times sweating.
Oh and denied the red wine marks on the living room carpet...when i dont drink wine.
He never used to hoover either. (this is key later)
I would say if its not a close friend or a friend you feel it could go either way with (not a life friend)...then do it, but make sure you save on the side if you can.
My scenario ended, when the bloke was rude to my sister (long story but they went on a date or 2...i know, thankfully shes now married to a lovely bloke)...she wasnt interested and this riled the guy...he also used to get drunk on a sunday and come in at stupid o'clock and fall up the stairs.
Well this one sunday he was really p*ssed and my sister came over, he was rude to her (well ignored her)...pulled him up on it...he went off on one...to which i lambasted the idiot. I gave him a few home truths, the best one was he said he always cleaned and hoovered the house...well he couldnt have hoovered as the hoover has been broken for 6mths and id been using my Nans....his face was a picture.
Next thing he wants to sell up....result...i bought his half for the same price we paid for it 2 years previous (3 separate valuations)....2 years later, we made 70k me and my fiancee...so it had its perks.
Blokes actually got a kid now....he couldnt even tie his own laces.
