You own the copyright. You can do with your photos as you like. You don't sell the images with stockagencies, you sell a license to use them. When you give some photos to a model you still own the copyright and the model needs to ask your permission to use them. The model is not permitted to sell the photos. When you have models in your photos, you can only use the images the way described in the modelrelease. You can show the photos on your website, but not sell them without the permission of the model. Other images: Sell them on your own website, give away a photo to friends to hang on their wall.... it doesn't matter...It's your photo.
The only exception is when you sell the rights of a photo. After doing that the photo is no longer yours and you are not permitted to use it anymore.