Affordable is the wrong metric to begin with. First, draw up a list (in conversation with elders from your church) of which are the best online programs for what you are looking for. Then figure out a way to pay for one of them. If you are headed for a lifetime of ministry, it is a poor investment to cut corners on your education. The cost of seminary classes is not that much when you consider the impact it will have on your ministry.
That doesn't mean the best program for you is necessarily the most expensive; not everybody needs the same thing from a program. But if you start looking for the cheapest, you are looking for the wrong thing. And some programs may have scholarships available that reduce the sticker cost considerably. If your elders are excited about you heading for ministry brainstorm with them about how you can fundraise, either from the church or individuals within the church and your personal network. You might be surprised who will chip in and how much they may give.
Personally, I'd recommend checking Westminster's online program out. It may not be right for you, but it is certainly one of the best, in my (biased) opinion. Feel free to DM me if you need more information.
