Huh, that seems like an odd rule-of-thumb. That would guide you to put more money into deals with lower absolute returns, which would lead you to really low ROI

Huh, that seems like an odd rule-of-thumb. That would guide you to put more money into deals with lower absolute returns, which would lead you to really low ROIs. eg, if you were willing to put down 66% on that property (£100k down, £50k mortgaged), then a £500 rent would be ok. Or am I reading that wrong? I am completely ignorant about UK real estate, so I might be missing something obvious.