W/D usually need 35' MH or more, its possible to get double units for faster service.
Regular driver licensees usually cover up to 26,000 lbs., CA under 40', larger MH need class B licensee.
Gas units usually have more basement storage.
Gas units are comparable to diesel in HP, diesel has more torque.
Gas engines are more economical to maintain.
Diesel engine last more miles.
Most MH 40' plus are diesel.
MH with tag axles carry more weight.
Cost of fuel and maintenance DPM (dollars per mile) about the same for gas or diesel.
Compare quality units with quality units, there are a range of models in each name brand.
Most all manufacturers will have (or build) models with bunk beds.
There are very few roads in the Interstate system that will have grades inclines that significantly slow down the average MH with tow.
Only one car would be pratical to tow, 4 down is best option.
A good solar system will pay for itself over time, saving on campground cost.
Use MH insurance and cover on board personals.
MH Roadside Assistance Insurance is a very good idea.
Important questions to consider: Do you have experience driving a large vehicle, can you drive towing 4 down and not being able to back up, how much floor space do you require, How many if any slides, what items are a must to carry considering the weight limit of the MH, will there be bikes etc. to carry, will one car be sufficient, will one bath be sufficient, proper space and lightening for class room study, budget, new or used MH, etc..
If you have more specific questions they can be addressed.
A must read for those concerned about engines: http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/17184035.cfm
