u/Due_Investigator2097

I need to build a portfolio so my plan is:

1. Ask the client to get in touch to communicate what needs to be built;
2. The client doesn't need to make the deal with me - they can start working with another bidder. In that case I will still complete it for portfolio and possible feedback;
3. Show them the video of product in work. If they like it and haven't started working with anyone else, they can buy the source code;

Is this a good idea? Will platforms like freelancer.com or upwork ban me?