This question always pop up in my mind. Any guide for this ?
i mae character, props, and weapon.
Adding/extending to what @franktech posted, people will usually pay attention on seller’s posts to see if he contributes with the community and also the quality of those answers would point if the seller has knowledge, so it is a way to measure one’s competency.
Price can be thought:
=> its cost must reflect your quality and competency == higher quality increases price
=> it must save time for the buyer, so he doesn’t need to contract someone to do it == lower price is an attractive
=> the more customizable == higher price
When to know it is ready, it is a strange question thou, because you just don’t create things from thin air, you create things with a purpose, to fill a gap of something that doesn’t exist or are poorly covered in a specific market, so there is no straight answer but a set of questions you should make to yourself:
=> Is it easy to use?
=> Is it well documented? (docs, pictures and video)
=> Does it interfere with other known system implemented in a game or archviz?
=> Used in a game or archviz, how much more work the user must accomplish to use it?
=> consequence fromt the previous question: Does it save work?
It is clear with the text above that when you provide just a character, there is no way for one to tell if he can properly rig or animate it later, so it is high risk for the buyer (no rights for a refund), meaning the chances are close to zero. But if you sell a rigged and animated character, then the opportunity for a sale is much more higher than zero. The risk for the buyer is mittigated because Epic would do some QA and for the product description they know they can complain it something doesn’t work, even giving them the rights for a refund.
thanks for info, i will study more 
its a huge wall for newbie like me.
i am however, only know how to make models.
Don’t get me wrong… I am not a super ultra dupper expert in Unreal… I do know my limitations in game development and I do know there are areas I can’t compete, because it is just not the fact of knowing how to do something, but do something with the quality expectations for a buyer and that can be on par with competition in the marketplace. This is the main reason why I don’t sell models (yet) because it requires knowing and offering complete solutions:
- model with excellent topology and texturing
- with bone hierarchy compatible with Epic skeleton (unless it is not humanoid, but will require bone hierarchy)
- rigged in a easy way, using common practices in the market (how to rig for several spots to move arms, legs, waist, head, eyes, mouth) and not having unwanted bends or twists in body parts.
- compatible with animations in the marketplace
Until I am not able to offer complete solutions like that, I will not enter the market, simple.
And this is the part I don’t want you to be offended… your question is far behind the one you think you should ask: How do you know you are ready to sell something?
I hope you can find a way to complete your study and become a complete professional (afterall you called yourself newbie). The market for employment does requires more than just a 3D Modeller, he must know how to texture, rig and animate, he does need thou, excel in something, lets say modeling or animation, and even thou animation nowadays for humanoids are completed with Mocap. There are people that excel in texturing, but don’t have same profficiency with modeling or animation, but they do know the stuff.
I do want you to consider some attention for the Udemy’s courses (there are lots of them) with prices that almost everyone can afford, just yesterday I saw a course for US$30. I myself made 5 courses in the end of last year, each one cost me US$ 10!! They are not mastering courses, but they do add to your profile.
If you want still compete with modeling, do props and weapons, since they have less requirements besides the scale which should be compatible with their intended use (ie: revolver scaled to a character’s hand)