I would highly recommend sticking to the 30 year option or not doing it at all. 

I would highly recommend talking to Jeff Weller at Coast 2 Coast and Fernando Corona both are also PadSplit hosts but we're some of the first expert lenders .

There was a news reporter at the sale and they interviewed the high bidder, who admitted that they had not seen the property, but were certain that they would be building their family home there. 

I don't have much experience with other platforms but I can assure you RentRedi sets the bar pretty high. 

Should I price the land 2 times above market value and offer a low interest rateORPrice the land at current market and use a very high rate?

The last thing you want is to have a home run deal that theoretically should be a high-profit flip but is ruined because your contractor screws you over in some form or fashion (late deadlines, inaccurate scope of work, etc.). 

They are buying NNN single tenant or NNN multitenant retail properties in TX, OK, SC, NC, GA, FL, AL, TN - the states to which the population is migrating and that have business/real estate friendly governments and lower taxes. 

I don't do this for a living and have no real world experience, but at 40% down, even with a 7% int rate, that seems like a high monthly payment.

This is a self directed RRSP or TFSA account that allows you to lend your money out to people with the backing of their mortgage for a high interest rate. 1st, 2nd, 3rd mortgages, down payments, refinances, flipping or renovation money.

Real estate agents are not highly regulated in Costa Rica as opposed to North America.