Of corse it give 30+30 years rent, you can get a normal 30 years contract and a option of another 30 years, I did that a few times for Factories and houses.
Only big problem is even you own it, if you allow some1 to stay in your property for over 3 years, and that persion dont want to leave, even he/she didnt pay rent, it will take you 2-3 years on Court to get them out.
So you could end up spending a lot money for lawers and seeing your GF living in your hosue with new fucker..........and not to easy to win a court case ike that, as you can not own that land legal so Court will decine that she have to Sale it and share it 50/50, but if she not want to sale, it will cost you again 5 years to get this down via Court order, things getting much worse if she has kids, than no Court will kick her out of that property, thats Thailand......