Mahindra Tractor and New Holland Tractor are indeed renowned tractor manufacturers known for producing high-quality tractors, and they have a strong presence in both the new and second-hand tractor markets. Here's why they are considered among the best tractor companies for second-hand tractors:

1. Reliability: Mahindra and New Holland tractors are known for their durability and reliability. This reputation extends to their second-hand models, making them popular choices for those seeking dependable used tractors.

2. Availability: Both Mahindra Tractor and New Holland Tractor have a significant market share in India and other agricultural regions, leading to the wide availability of their used tractors. More availability often means more choices for buyers.

3. Dealer Networks: These companies have extensive dealer networks, including authorized dealerships that often offer certified pre-owned tractors. These certified tractors are inspected, refurbished, and sometimes come with warranties, giving buyers confidence in their purchase.

4. Parts and Service Support: Because these companies have a large market presence, finding replacement parts and accessing service and maintenance support for used Mahindra and New Holland tractors tends to be more accessible compared to some lesser-known brands.

5. Resale Value: Mahindra and New Holland tractors tend to hold their value relatively well in the second-hand market. This can be an advantage for both sellers and buyers.

6. Diverse Models: These manufacturers produce a wide range of tractor models suitable for various agricultural tasks, allowing buyers to find a tractor that fits their specific needs in the second-hand market.