Per project or per hour depends on the client. They often have a preference; in large companies, they may be able to get a "per project" budget approved, but n

Per project or per hour depends on the client. They often have a preference; in large companies, they may be able to get a "per project" budget approved, but not a per hour budget - so be it. You have to be a little flexible. What I used to do when I contracted was to estimate the amount of time needed, and then say X weeks * Y$/hr = total Z$ project cost. You learn to pad that, depending on the client, to calculate in "unexpected" costs. ie. for a difficult/inexperienced/unknown client, I would double the estimated hours. Both as a contractor and a client, if there is some trust in the relationship, I much prefer per-hour based jobs. But it's not always possible. If you bring in other people, don't hide it. There's no need to.