I'm totally new to woodworking and as my first project I want to make a small table. I'm planning to paint it so the wood material will not be visible. And I want to bevel the edges using a router. I'm trying to keep it on a budget since it is just a practice. There are several board materials I can use with almost the same price. OSB, plywood, MDF, and hardboard. I read online that mdf is stronger than plywood and OSB. But I can't find any info on the strength of hardboard. So my question is, if I use two layers of 1/4 inch hardboard, would it make a stronger tabletop than 1/2 inch MDF? Thanks.
ANYTHING is better than MDF for your project as it is a terrible material for furniture, especially custom made furniture. Also you can't use a router on MDF - well you can but it will not turn out well.
So you can probably find pine, oak and cedar at big box. All stronger than mdf, all suitable. If you are painting, pine is my go to as you can cover it without seeing the grains. (there are many many other choices of solid wood planks if you want to order or go to lumber yard. I just answered the question in a wood that is reasonably easy to find.)
I've used MDF to make a table top. (the legs, and upper frame were pine) the strength was fine (I jumped up and down on it etc) I didn't paint it because I wasn't going to do anything wet on it, and I didn't want to have to wait for the paint to cure (which can take weeks after it has dried) if you don't wait things will stick to the paint if left on the table.
if you do paint it use a two part paint because they cure rapidly.
Plywood and OSB are both stronger than MDF, but they have more surface texture.
Gluing two sheets of hardboard together without using a table-sized press sounds like a tricky task.