Revenue growth isn't tied to interest rates, it's tied to supply and demand in the rental market, plus what other comparable properties are charging.  

Look at mobile homes that are that age already and see what they are valued at and compare to their original purchase price.Is this located in a mobile home park?

What are the advantages/disadvantages compare to other types of real estate investing.  

Paying an attorney is still a bargain compared to a problem tenant. 

Tell them to look at local listings which are comparable in terms of rooms.

Compare an extra hundred bucks a month to having to do a $10-15k renovation now, between tenants, and in a year after the new tenant leaves. 

All of these factors will pay off disproportionately over time compared to what it took to get them and is worth the time.

Now before you guys go thinking I haven't looked for this.........I have, but I love to have options on the table especially so I can compare. 

Look up comparables and come up with a real After Repaired Value.

Clearing land/leveling a lot costs are small compared to the whole build so it won't be enticing for a builder to split his profits, Amazon plants/fulfillment centers are popping up everywhere, won't have any affect on the market.