Strong and sturdy .

__________________________________This picture right here can teach us that, that sink isn't as sturdy as you think it is.

My initial instinct is to tie the dog down with a leash that still gives him free reign of the yard, but I fear a dog that can jump the fence may be able to just rip the leash out.

Some markets are high-end and expect high-end finishes but most markets are looking for something that works and is sturdy; looks are less important.

You can try marketing it yourself but give yourself a short leash say a month.

Support - I will be asking the builder if the floor will be sturdy enough to support everything that comes with a bedroom3.

I don't work in the rental rehab space, only flips.Personally I like to do accent walls, wainscoting, crown/trim work, accent tile, functioning kitchen spaces, wine racks, wine fridges, etc...For a rental I would probably avoid all of this and go with basic, clean and sturdy over fancy and nice looking. 

My personal feeling a lease is an agreement not a metal leash.

This avoids the issues you get when taking on tenants that were not properly screened by the old landlord.Your only option now is to walk away or push current owner to evict or move to cash for keys. it may be to late to request the unit be delivered vacant, but if not that's what I would suggest doing. if you follow through with the purchase, keep this tenant on the shortest leash possible and start saving up for the (very likely) eviction cost.

IE special landscaping care to prevent dead grass, forcing the tenant to obey leash laws, requiring copies of shots, and licensing of dogs, forcing tenant to have additional insurance for the dogs that protect you?