He's not interested in a slot in an RV park. 

I also did the prior advice and booked 15 minute slots which did work out so I didn't have long wait times.  

We have thoughts to increase the GLA or add a DADU.

It will be pretty tough to find at this point.You are essentially looking for an existing house with a big enough lot that will either allow a DADU or can be split into 2 lots.Honestly, I think your best bet is to buy some land in one the suburbs and build your own house that has an inlaw suite. 

@Leon Lai, I'd start by talking a thorough look at the zoning code regarding the lot and design requirements for an ADU, I'd also confirm that they are interested in building an ADU (attached to the house) as opposed to a DADU (detached backyard cottage like thing) as the requirements and considerations will be different.

I would suggest finding a short term rental  that is ideal for your particular situation and buying that with the plan of renting it to the next guy filling he school slot.

For those interested send me a private message with some time slots and I can setup the 1st one.   

We also did consolidation loans to lower our rates and free up loan slots (you are only allowed 10 Fannie Mae loans per person in the US).  

You should always looking into single family houses or multifamily, as there is an actual land that you own and potentially build ADU/DADU in the foreseeable future.Also, the beauty of FHA is that it allows you to put 3.5% down payment to invest in 1-4 units.

We will also be building a DADU on the property and forming a condominium association to sell each one seperately.