Wondered if you have ridden in many carts? For fun driving, you certainly want to consider your own comfort! Hate being discouraging, but many of the metal easy-entry carts have a terrible ride, along with you not being able to see ahead of the horse while going down the trail or road. Leaning sideways the whole drive will give you a stiff neck. We had to sell our sleigh after getting a taller horse, because we could not see ahead.
You will want a seat back to lean back against, give your spine a rest. Seat cushions are nice but the board seat SHOULD have some kind of good springs under there to make the ride comfortable over rough ground. Little coiled springs, bent metal C-springs under the seat, do not really soften the ride at all. A hard riding cart will take the fun out of drives pretty quick.
Next will be the length of your legs to the floorboards. You actually need to be able to sit with feet forward from the knees. Not the 90* angle like in a chair. This lets you brace your feet to stay more firmly seated during travel, along with being able to move upper body forward and back giving and taking up reins, rather than suddenly hauling up on the reins with your arms. Short-legged people will add footrails or boxes to put feet on for that solid seat position. Longer legged people may need a different cart, not enough room to be comfortable in a proper position. We have modified our vehicles to gain better foot positions. But do not accept a vehicle that won’t let you sit properly, is too short or small, you will never be happy driving it.
We had an antique one like that, just TOO BIG for us! We are regular size, not big or small. We made jokes that the man who had it built must have had a 38" inseam, along with being a LARGE person. If we sat back, our feet stuck out like children in an adult chair!! Could not reach the floor with feet. Putting feet on the floor meant you were almost half-standing up! Carriage was in original condition, rode like a Grampa car, never felt any bumps, great view ahead of our tall horses. But vehicle did not fit US, so we sold it on.
Are tires air filled? They may be old, need replacing even though they look good. Like trailer tires, they die of age, not because they were driven on very much. Check all the nuts and bolts for rust and wear, especially the singletree and axle bolts. They DO wear thru, break off under stress. Often safer to just replace them all for safety with appropriately hardened bolts and nuts. Not all nuts and bolts are the same hardness! Metal shafts should not be able to be “bent to fit” or show signs of being bent back into place. This causes metal fatigue, which lets metal break off. Like bending paperclips until it falls apart.
Driving is exciting enough, without adding equipment problems! There are ALWAYS more/other vehicles available to buy. Very few vehicles are one-of-a-kind unique. So don’'t be afraid to pass on one, keep looking. 2-wheelers are safest for starting out horse and driver. But as he gains skill, knowledge, dependability over time, you may want to move up to a 4-wheeler for the better ride, holds bigger picnic baskets! Ha ha