This sounds like an exciting venture and a worthy cause, EdTech is a hot space right now, and rightly so.
Something to consider first of all is whether you want to build an MVP or a basic prototype.
If you are digitizing something which already exists, and therefore the need and model is proven in the real world, then it might be worth building basic foundations with a prototype.
This means that you can then build on it as you learn more about how your customers want to use your marketplace.
If cost is a major consideration then you might want to "fake it until you make it" i.e. create a slick online proposition but leaving out much of the plumbing in the background initially, and doing the background operational functions more manually.
The additional benefit is understanding how the marketplace will operate before translating that into product requirements, I used this method for over a year initially when creating a marketplace and it served us well.
The more "perks" and functionality you want to add the more cost will be involved, just focusing on the basics and doing those right is best as often when it's not clear how users will use the marketplace you can end up creating functionality that isn't used.
This comes at a cost both financially as well as time-wise when you could be developing other stuff.
It is important not just to think about the technical/product solution which is exciting and fun to do but the overall business.
In terms of funding one of the approaches might be:
1. Self-funded/friends and family - until something tangible to show e.g. MVP
2. Angel funding
3. Angel/growth funding as you scale
Unless you can bring onboard a technical cofounder who will build for equity or you can access government grants or similar support funding.
Marketplaces are capital intensive, require a lot of marketing and a lot of throughput, something worth considering from the outset.