the pictures aren't detailed enough to see, but my first thought would be that it's a commercially built trailer, and not a homemade trailer. when people build homemade trailers they often utilize used mobile home axles and end up with trailers of varying degrees of safety and capability. when a commercially made trailer is constructed, the manufacturer doesn't steal the axles out from under billy joe jim bob's house, he uses a commercially built and rated axle. in past years there were many trailers built with the same wheel/hub style that is used under mobile homes. just because they look the same doesn't mean they should be called mobile home axles. would you call the nimitz a boat? if that is in fact a commercially built trailer, then it has trailer axles underneath it, and not mobile home axles.
i have a pair of 9-14.5lt heavy duty low boy load range f tires here that are capable of carrying 3250lb each at 100psi. they look just like mobile home tires and wheels, and they will even bolt on to my homemade trailer that has mobile home axles and wheels. these tires are likely the same ones that are on that triple axle. i find trailers with that style axle to be a great setup for the occasional tower. if you are gong to use a light duty trailer 300 days a year, then i'd probably consider a conventional style for convenience. anyone that would consider converting a used trailer with that style of hub to a standard trailer wheel/hub should have their head examined. you could buy the used trailer you are trying to make for less than the cost of buying new axles, hubs, wheels, and tires.
as far as buying and using that trailer goes... it's probably a suitable trailer - if you were puling it with a ton truck. it really seems a bit much for a half ton. even with the tractor and implements you have now. i'd be amazed is the trailer wasn't heavier than everything you plan on towing. good deals are hard to turn down, but i think it's a little too much trailer.