THe best thing I ever built was my contracts. Make sure you have tight contracts (easy to do in Jobber) so do one can try to pull that on you after you perform a service. As far as low balling on the front end, everyone learns this one the hard way. Lose enough money on enough jobs and you will become desensitized to low ballers haha. Once you know what you can't do jobs for, it's really easy to politely tell someone that you will pass on their job. I tell people all the time now "dang sounds like you got a good deal then!" and just let them go on their way. Half the time they still come back! It's crazy. We run businesses not charities so don't take their low balling personally and just politely pass on the work.
