@Account Closed it's a great question and I had the same question - except I was on the other side of the equation (I was the Realtor, acquisition and finance partner) and when I first started I couldn't understand why a contractor would want to partner with me. Funny to think of it like that, right? :)
But I still prefer partnerships rather than going on my own. The reason I love partnerships is because everyone's goals are aligned: we all want to sell/rent a property for the most money and find ways to reduce expenses where possible, and I want to partner with people that I lack expertise in.
You hear all the horror stories of terrible contractors that runs off with the money, does terrible work because they don't care, etc. Well I know when I have a partner (that I trust - which should not be minimized) I am comfortable that he is going to perform her/his task best and I can focus on mine - which is not babysitting contractors.
Hope this helps and if you find a good partner I really recommend staying with them as long as possible, and not to get greedy. Complimentary skill sets are great.
(Last thing I will say is TRUST, personalities, and set expectations upfront so there are no surprises.)
Best of luck!