If the land is included with the mobile home, there are DSCR lenders that will be willing to lend up to 70% LTV as long as it is not a rural area. 

I was wondering if there were any builders who have any good strategies on where to buy land when you're looking for spec homes.

Say my neighbor wants to buy a 1 millimeter strip of land along our shared property line for 450k. 

What you spent on the land/lots can go towards your down payment and, if you've owned the land for more than 6 months, you can use the value of the property toward the cash injection requirement.

However, since I am hoping to sell the land first.

As far as some other comments about like kind etc, you can sell this SFR and then buy a warehouse, or vacant land or even exchange into a DST there are many other assets that are considered 'like kind'.

as one who grew up in the land business brokering land in Napa Sonoma Lake Mendo and humbolt counties..

I'm a new investor from Melissa, Texas, primarily interested in multifamily properties.

Entity structuring, basis calculation (i.e. breakout between building and land), deductible expenses, etc.

I just landed my first property (woo!)