Checked your site, nice info on places like The Villages, though having to use a bottom slide bar to read was a minor irritation. 

Depending on the extent of your rehab, you can buy used windows, doors, vanities 1st and frame around them.  

If you are unable to accomplish them within the time window, move on and come back. 

And they usually will let it slide 1st time.

Few examples;I know a guy who lost a large window manufacturing company built by his father.

Check out the floors around the outside walls and windows for soft spots which are usually common for mobile homes.  

I will purchase as owner-occupant, and transition it to a rental after the 1st year window of ownership has passed. 

The house is framed, roofed and sided with windows and doors in place.

I was curious about the gate thing, so I did a quick search and found this option (no idea on the price but it looks like it would do the job):http://www.ameristarfence.com/adaptrack-sliding-gate-conversion-kit

It discussed estimating repairs, they gave us their price sheet for estimating repairs (with specific numbers to use for windows, floors, paint interior and exterior, roof, AC/Heat, Kitchen, Bath, landscaping, etc.), it went over hiring and dealing with contractors in a professional rehab with timelines and change orders, they discussed obtaining private money, hard money, etc, they talked about different ways of finding properties to buy, they talked about having exit strategies in place in the case that it wouldn't sell, having a project manager....that's all I can think of right now.