Hello to all, colleagues and readers of the forum! I apologize in advance for my English as I don’t actually speak English and use a translator. I have an average experience in the field of 3D modeling and would like to offer as an example my work. Perhaps someone will think that one example is not enough, but I ask you to appreciate my work! I will gladly take part in someone’s project as a Builder, but I would like to talk about this personally on my twitter - twitter.com/yarikkot1698. On account of their work, but I’ll just say that the job was done in about one week, the work was done on existing real-life building - the Russian old Russian water tower (if you want to compare my work with the original). The roof was slightly changed, the flag of the USSR was added and a brick crumb was added (all this was not manually done, but added from roblox studio). The whole tower itself was built clearly from the photos of the already existing tower (Russian old Russian water tower) with the possibility of entering inside. If my work can interest anyone, I will be happy to chat on Twitter. Waiting for an adequate criticism! You can find my work at the link below!
https://imgur.com/a/ULBUOPw
View job closer by the link - www.roblox.com/games/2874763354/Dying-Hope.
Contact me - twitter.com/yarikkot1698.
Since I have average experience, for the work I will take no less than 20% of the earnings of the game.
You forgot to add your payments,contacts,availability. In your post!
I think I added everyone, if I missed something please let me know.
If you want to be hired communication is the most important thing. If you want to get hired you should make more buildings. When someone wants to hire a builder he/she must say ‘Wow!’ when he/she sees a portfolio.
Okay, I hear You! Thanks for the advice, but I don’t know what buildings people are interested in, I can build buildings from photos, I can build buildings from pictures, descriptions, etc.
You should be creative! 
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Hello!
As @kacper532 mentioned, you should include more examples of work in your portfolio.
The goal of making a portfolio of any kind (GFX, Building, Scripting e.t.c) is to display things that you can create at your best, and achieve a positive atmosphere that will wow other developers. Doing this can attract developers that may need someone of your type to hire.
From my perspective, it doesn’t matter what you build on a portfolio, as kacper532 mentioned, you should be creative. 
Taking references is perfectly fine, but from there try to change up some things, maybe make additions or change the shape of the building. The possibilities in developing in ROBLOX is limitless, and I urge you to explore how creative you can be.
This is kind of a personal recommendation, although not needed, I think it’s quite important.
Practice on multiple building strategies, try improving on building realistic items and buildings, and then once you’ve felt like you’ve improved, try go for building in Low Poly. Developers like to see what others can achieve with what skill they have, and depending on the skill you can, you can get a ton of oppurtunities with both known and well-known developers!
Hoped my tips gave you an insight as to what to work on and accomplish. 