I think some are good like they will do pure business they will think of there profit as well as requirement of the person they are doing business with they will do things which will be benefited for all whereas some are bad and they only look for there profit how can they make more money out of deals. Depend on a person and on his tendency.
That's far too diverse of a question to even answer with a yes or no.
Fixer uppers involve a number of levels of risk. There are many things one needs to depend on to lower risk .. Like expertise on evaluating what would be needed to produce a favourable end product (for example). Even the most experienced can discover things they missed or could see during an initial inspection .. That are only revealed once desruction starts. Wiring issues, infestation issues, structural issues .. Can often be hidden until you start taking things apart.
It's an 'educated guess' when it comes to choosing which project to take on and which to walk away from.