This trail is a bit tricky to navigate due to the rock-cut steps and steep slope. However, the difficulty level is medium, requiring basic physical endurance. Do note that the trail becomes tougher to tread through during the monsoon as the steps become slippery.
DIY or not
You can do this trek on your own or book it with a travel company. If you are travelling on your own, don't rely on Google Maps as it takes you to the Kalavantin Durg Peak through a dense forest, which is not recommended. Instead, get on the Mumbai-Pune Expressway and get off at Shedung. From there, ask locals directions to Thakurwadi. They will also be able to help you with the route to Kalavantin Durg.
While you can do this trek on your own, taking the services of a travel company is recommended as you won't have to worry about checking for directions, and there is always a general sense of encouragement and togetherness when you're travelling in a group. This is also a great way to meet some new travel buddies, especially when you're travelling solo. Treks And Trails India, Mumbai Hikers and Trip Hippie are some companies that arrange this trek.
If you're trekking on your own, the only expense you will have to make is on getting there, which should cost you as low as ₹150. Travel groups, on the other hand will charge around ₹800 to 1000. Some companies offer overnight camping and bonfire at the fortress, which is included in the cost.
When to do it
October to March is the best time to go. Monsoons are pleasant too, but heavy rains can make the already dangerous trail difficult. Avoid trekking during summer as it's really hot and humid.