I fall into a similar problem in the winter. I do my hill sprints up on the hiking trails so when it rains, it gets messy haha need about 3 days of dryness to go up there.
Luckily, I have a sled. Check on ebay. That's where I got mine. About 50 bucks. After buying rope, a harness, etc, it was still less than a hundred bucks.
If that still costs to much, try your hand at building your own out of an old tire.
Are there no high schools with football stadiums with stairs around you? That's where I've ran my stairs (just be careful after it rains if they're metal stairs).
Last but not least, settle for complexes I guess?