How to reassure others that you can handle it?

This year, I have a goal for myself to buy an investment property. However, my husband often thinks that we’re too busy to be able to take care of our full-time jobs, two kids + real estate investment. I have tried telling him that I would handle it and that if he doesn’t want to be involved, I will do my best not to involve him so that it doesn’t negatively impact on his schedule and on his regular job. He feels overwhelmed by the amount of work he has on a regular basis. I have tried to tell him that overwhelm is a feeling that is caused by his thoughts and that he can work on his thoughts not to feel overwhelmed, that there strategies he could work on to deal with this feeling. Clearly, I am not doing a good job coaching him. We’ve had a lot of arguments over this. In one recent discussion, he even asked if it was conceivable that my being in SCS has led me to a goal that is overly ambitious for myself. I don’t feel overwhelmed, although I would like his support in my pursuing this goal. I think I can handle it, but there is a small part of me that does believe that having this additional responsibility of taking care of another property will have spillover effects on his job despite my best efforts (mostly because he’ll have to take care of the kids while I’m busy). How do you reassure someone else that you are capable of doing certain things? How do I prevent this conversation from happening again and again? Thanks!! Yvonne