Build me a website like BrickEconomy and add the sell/buy function from StockX

I need a website like BrickEconomy with a function of the StockX website, the function is Buy/sell option. Some background info about the website: About the website: The LEGO investment phenomena has become a highly collectible and profitable hobby over the past ten to fifteen years. LEGO investing and collecting, the values of sets and minifigs exploded in growth in direct correlation to the popularity of secondary markets such as eBay, Amazon as well as specialized LEGO sites such as BrickLink and BrickSet. Up until the 1990s there really were no major outlets that a person could resell LEGO sets or minifigs, so when secondary markets such as eBay grew in scope and popularity, savvy collectors realized that sets could be sold for a profit. Since then, coupled with the LEGO Group’s decade-long run of extraordinary profits and growth and their expansion into the Asian and Middle Eastern markets, the LEGO secondary market has exploded in growth over the past decade. With the LEGO Group’s continued production of creative and innovative sets that are of the highest quality, the future is very bright for collectors and investors. With typical investments growing at a rate that even outperform the national stock markets and various exclusive and limited sets growing at well over double-digit annual rates, investing in LEGO is a very viable option. What is the website about? The biggest issue for LEGO collectors and investors is trying to accurately track the current value of a given set or minifig. There are dozens of disparate websites (and physical markets) that sell and resell retired LEGO products making it difficult to get an accurate understanding of the potential growth of a set or minifigure. This is where BrickEconomy comes in. BrickEconomy is a comprehensive site dedicated to analyzing the secondary LEGO markets and determining the current and expected values of both sets and minifigures. By using several technologies, specifically Machine Learning, BrickEconomy, digs into the data and helps investors truly understand the value of their investments. BrickEconomy ('Brick' + 'Economy') is the economics of LEGO (brick) investing. How does website work? Our background is in economics and complex data science in other industries, but we are massive LEGO collectors and apply our knowledge to understand the economics behind LEGO collecting and investing. That said, BrickEconomy is all based on data, and a lot of data. We mine dozens of online resources to continually look for LEGO sets and minifigures that have been sold through both secondary and primary markets. Prices are constantly updated, and we leverage proprietary algorithms and machine learning models to accurately predict current market value of time as well as expected growth. Our large data sets allow us to train a variety of machine learning models to give you the most accurate, up to date intelligence to help you better understand your current collection and help you make the best decisions for future investments.