Offering massage to a straight guy? Thoughts?

I have done massage on and off as a side job for quite a while. I've worked on quite a few straight guys doing legitimate massages. Many of them become aroused and in a professional setting, you just ignore it. But in a more relaxed one, like working from home or at their place, things like happy endings can result. There is a straight married guy around 30's who is very fit and who lives a couple houses down. He actually cuts hair out of his garage. He's very fit with workout equipment in the garage on the other side. He's always walking around shirtless in front of his house in the warmer weather. I asked him to help me move a heavy box and purposely left the massage table up in the living room. He asked about it. I explained I did it as a side business. A couple weeks later he was on the table. I just expected to work on his nice muscles but he stripped everything off and let's just say his happy ending made me happy too. He was shy about getting a boner at first. I said it was normal. When I started massaging around the tool, he looked up and I said, "you don't want a happy ending do you? as a joke. He said if I wanted.

So, let's just say that touch can arouse a man, even a straight one. But you have to be careful and always respect boundaries and ask for permission.
I’m curious your thoughts about how to make things happen in an informal environment without being creepy. It seems like you both handled things perfectly. Wait and see if the massage therapist initiates things?

(Perfect post, by the way. Helpful and stimulating. )