Are my models good enough for selling?

I started modelling about a year ago so i may not have a good idea of all this but i think your work is very good! Also some models maybe could sell at a higher price. If your model's price is set too low people may think there is a lack of quality.

You likes/views ratio is pretty high and your models look very good. I think you can do very well if you manage to lower the poly count in some of your models. Like that HK 416, it has 700k faces, that's very high even for high poly models. If you do a version under 20k and bake the details using normal map, it will be a lot more attractive for buyers.

Also, this house,
https://www.cgtrader.com/3d-models/exterior/house/oggy-house
could be marked as low-poly.

Low-poly doesn't necessarily means the flat, big, blocky polygons style. There's not a strict rule on that. I generally ask myself if my model, given its size and purpose, would fit in a modern game, if so, I mark them as low poly.

IJust wondering what software do you use mainly for your models? I started a few weeks ago so I don't really have any suggestion redagring the models themselves, but i noticed you have the marmoset 3d preview on some model which can be very useful to put on more of your 3d models to make them shine!
PS: The basketball court looks really cute!

If you are making sales then someone find your models useful therefore they are good.