Is it possible to make an army for free?

Ok so maybe not for free, but with miniatures you've got that have never amounted to a full blown project.

This also includes spare bits.

Tonight I'm going to sit down, and start the ball rolling on a project that will cost me not a single penny from here onwards.

Now already I know that I have access to a certain number of items such as:

There forge world rifle dreads.
A hellbrute
10 terminators
A librarian in terminator armour
20 cultists
About 15 or so marines of different

And of course a bits box.

My initial idea is a nurgle esq army. Based around the more mechanical side of life, where a daemonic plague has ravaged everything in sight, corrupting everything, once something has been infected
It dies and is reanimated by the warp.

Initial ideas are revolving around the dreads being used as daemon princes etc

So opinions guys? Can I make an army with fluff made out of unused models. And also can I make it into something that plays one the table!