Unfortunately, or fortunately, small multifamily are valued usually on the comps What is a typical duplex in the area with same # beds, amenities, etc. going for.

They generally end up with better options than a lower income self paying tenant.

Will I read somewhere from a realtor that modulars had the same resale values as typical homes.  

I just posted about it here:https://www.biggerpockets.com/...It's been an excellent option for me. 

Being in a price point that typically caters to moderate earners, so affordable to their incomes, but also having a tenant base that is more likely a renter by necessity than choice (or the non-PC way of saying it: a tenant that can afford your rent without struggling, but can't afford to save up to buy a house).3.

The cabin belongs to an acquaintance who doesn't want it anymore and is giving me the option to purchase it before putting it on the market.

(Ive checked "some" other options but came back to these) - I have qty18   5-year Balloon type loans for my current portfolio. 

I agree with just about everyone above that the price should be either discussed upfront or in the engagement letter before services began.It's different to know how much they saved you because tax preparation typically isn't a service to save you taxes, you'll want to meet with them during the year for this.

I am having trouble finding options for a pre-made triplex mailbox.

If you're willing to use a good bit of the $500k as a downpayment, your options would be limitless for Hocking Hills!