If you’d like to go down the podcast sponsorship route, there are a couple of ways you can do this. 
There are two main ways you can approach podcast sponsorship.
Firstly, you can work directly with a brand on a bespoke brand sponsorship deal. 
In this scenario, you would pitch directly to a brand with a strong alignment to your podcast (and your audience) and broker a deal to work with them.
Bespoke brand deals usually occur when the podcast content has a clear, defined audience and the brand’s target audience aligns seamlessly with the listenership. As a result, the brand would be reaching high quality, engaged listeners in their target demographic. 
The commercials of deals like this vary enormously, as do the sponsorship deliverables. 
Secondly, you may like to explore dynamic insertion platforms such as Acast or Audioboom. The platforms source sponsorship on your behalf and dynamically insert ads (both spot-ads and host-read ads) into the content). They then take a percentage of the sponsorship paid. 
These platforms usually start working with podcasts that have a critical mass of around 10-15k weekly listeners.