Have you ever considered a low start-up cost business in the concrete industry?
Consider this small batch concrete batching operation.  U-Cart system: Operating 25 Ton Silo 3 Hopper Delivery System: 1-3/4 yard U-Cart concrete short load operation with 6 trailers: 4-1 yd. & 2-1-1/2 yd. Includes bobcat.
This plant can provide you with a very nice rental business focusing on contractors. 
Concrete equipment - used