There is a lot of ways to sell your value to clients. I would start off by creating a store of pre-made floor plans.
Building the store will give you the advantage and create the oppurtunity to show your skills and also create the possibility of selling the floor plans to make money.
On this store of floor plans I would create a strong call to action that makes customers aware you can do any type of custom design they can dream of.. Using a lead magnet to capture customer info.
If these are high ticket floor plans it may take some customers days/weeks/months to pull the trigger. Make sure to have a well written and planned email funnel setup to try and convert every single lead.
I would target end users first. This will build the demand and will make it easier to attract agents.
Instagram & facebook would be ideal places to show off your work too and build a build in customer base who will help spread the word of your skills just by sharing your designs.
I have brand names that sell digital products in the same manner you are looking to do. I can help you along the way if you need my help Im just a call away.