A small tractor, a Class 6 might do, pulling a 40-foot low-boy trailer with ramps. On the lowboy, a one-ton SRW pickup with camper, for camping, and moving the boat around at the ramp. The pickup hauling the boat trailer should fit on the flatbed, leaving some room to ride the bikes on.
A class 5 or 6 flatbed might haul an adequate trailer on a gooseneck, we use them at 20,000 pounds here pulled by even lighter flatbed trucks. Then you could possibly put the bikes on the bed ahead of the gooseneck. My uncle's toys were cars and bikes, and he would take two cars and several bikes with him by putting one car on the bed of his truck, and another with the bikes on a bumper pull auto trailer (about 10,000 pounds on the hitch). Or he could put two cars on the trailer.
Buying really well used might get under a $60K budget. $10K for a high mileage truck with a bed or a fifth wheel, $6,000-8,000 for up to 20-ton lowboy (a lot less for a gooseneck flatbed), leaving $40,000 for the RV part of the budget.
Living quarters are going to be really tight in a truck camper, for full timing.
The larger toyhaulers, or Haulmark type conversions, are really a better fit for your needs, except that I see potential for problems at the boat ramp.
This could also be an issue with a frame extension or bike lift on an A. The A would likely be a diesel pusher, in order to have adequate frame for the load.
I'm also seeing this as a potential goal for a schoolie conversion, a 60 passenger bus should have room in the back to haul bikes, while still space for living quarters forward of the rear axle. The frame will have adequate strength for trailering a boat that size, and would be less of a problem at the boat ramp, compared to long overhang, low to the ground motorhomes.
Considering the flat bed truck and slide in camper seriously now.
I would get it registered as an RV since it will have stove, sink, toilet, bed, etc. This may reduce insurance and the need to stop at weigh stations.
Looking at a Fuso FE with an 18 foot flatbed, possibly mated with a Northstar slidein meant for flatbeds. Used Fuso and new Northstar would still be under 55K. The FE has a GVWR of 17,900 lbs and a payload of over 11,000 lbs so should easily handle the slide in plus the two dirt bikes.
I have a little experience with this "toy hauling" so I'll chime in. If you plan on extending the frame of a class A there are some things to take in consideration.
!) you need a diesel pusher tag axle coach not a traditional bus either (the wishbone's on your typical Prevost will not handle the weight and you chance cracking the vehicle in two parts) but one built on a truck frame. Most of the latter have a 10,000 lb capacity for the tag AND USUALLY they are only using 3000#'s of it.
2) the further out you go the greater the applied force becomes on the rear axle of a given weight.
3) there is a maximum length in all states at 45 foot. If you modify the chassis and place a platform on the rear that cannot be removed I can't see how you could get around the laws.
4) Even if you don't get stopped what would happen if you get in an accident and it is FOUND you are driving a vehicle that has been modified and is over the limit. Traffic ticket?? Denial of insurance??? I don't know just sayin'
I say this as I carry a 1100# m/c on the back of my Discovery (single rear axle.) I am close to the DOT limit of 20,000#'s. The lift is removable but it adds to the 41.5 feet making the overall length 47.5 feet with the lift, spacing and tow assembly on the end.
Well, we have now bought a 2006 Isuzu NRR cabover diesel flatbed (20 foot flatbed with 19,500 GVW) and are committing to building our own toyhauler. Actually we are going to CAD the structure and have it professionally welded/aluminum skinned/painted by a company with lots of experience in custom jobs. I will finish out the interior in African hardwoods, as I have tons of board feet of wenge, bubinga, mahogony, and even some ebony. I would just be junking it when we sell the house anyway..
The plan is a modular or pod system, somewhat like a truck camper but with no side scoopouts since we have a flatbed. It will overhang the Isuzu cab like a class C but will drive like a class A (actually better than a class A). There will be two pods, one for living and a rear pod for toy garage. The rear pod will be line-x coated on the floor and part up the wall, and will be capable of holding our snowmobiles and dual sport motorcycles at the same time. When the cab needs to be tilted, the pods can be removed from the flatbed via jacks or the front living pod can simply be raised 11 inches on the jacks to allow clearance for the swing of the cab. If the truck needs to be used as a flatbed or serviced for an extended amount of time, the pods can be removed and placed in a base camp for living on the ground.
Driving the Isuzu sold me. Even with the 20 foot bed and the 19,500 GVW, I felt like I was in my car. I was able to do a u-turn on a residential sub-division width street even after just a 5 minutes practice on the test drive.