lots of these anecdotes are about buying a house and living with a friend whereas the OP is talking about buying a buy to let with a friend - much less drama and potential for going wrong
don't see the issue providing your friend is not a muppet and you both treat it as purely business, set out what happens in advance in a range of scenarios like one party wanting to sell, payments for repairs and periods where you can't rent it etc..
though one thing I would query is why you need to go halves with a friend, why not just get a cheaper property yourself, the yields tend to decrease for higher priced properties. though I guess there are some advantages in buying say a flat in Canary Wharf in the form of more reliable tenants - you make sure it goes to a financial services professional who'll be easy to track down and won't want any CCJs against his/her name as it would ruin their career.