Make sure you get paid.
Don't give anyone more credit then your willing to loose.
Don't leave yourself liable for unsafe conditions or repairs not made - ducument and get signed.
Don't think about the promices of more work to come. Price each job fairly. Don't price low so you can get the next job with the person.
Don't back down on your prices. They want to pay less then maybe you could offer to do not as much work.
Associations can waist your time. They may want a bid on some project. You need to figure out the details like how many fixtures they have on each building. You do all the leg work. Wait for a meeting. Then some want the price broken down per unit because their unit is a shorter run to the panel, or their building has less fixtures. So they may want to see every unit charged a different amount X how many units. It can go thru meetings for months. In the end some can never agree on anything and nothing is done.

Tom