We are almost finished bulding our 2nd prefab concrete and steel home at the farm. It takes 90 days minimum to build any prefab house if nothing goes wrong like, rains, floods, availability of supplies, workers show up, you have power. It is the rainy season right now. If it only takes 88 days to build, your lucky. Allow 90+ and be safe at least in your head.
The foundation: That is assuming site work is done. Such as your pad is raised, so your not flooding when the rains come. Remember, as a foreigner, your standards are higher than theirs, much higher, it just is. Our caretaker house was supplemented with a house pad made with concrete blocks and rebar, filled with river rocks and then stuccoed. This added to the time involved and the cost. Our farm crew gathered all of the rock from the river, truckload after truckload. The package price just builds it there, wherever there is. You still must remain smarter then your "contractor", and always be thinking a week or more out. If not, you will get what you get. The caretaker house without the foundation we put in would not have been a good thing. They contractors would have put it there however, no problem.
Make sure the exterior doors are exterior doors. Locks, you pick them out or hire a lock guy. Make sure they open the way you want them to, I swear no one here is thinking about how doors should open. When you have a small space you needed to use that interior space for you, not for your doors to swing in. Have a large overhang over every exterior door, so the door and people under it stay dry. Perlin does not attract termites, we use it. Termites are a problem in the rainforest. We used fibrolite (concrete board with no asbestos) for our ceilings, I like it and it can be interestingly arranged. Later we may add a bamboo ceiling over it. Your ceiling does not need to be a flat one inside your home, it can be cathedral like. Ours is, our caretakers is not. Add insulation to the ceiling. It is an extra cost, but the rain is so loud you can not hear yourself think, and it eliminates (or helps to eliminate) condensation.
There is no problem with prefab homes, the problem in general is a Central American culture problem, no one is thinking beyond this moment, in many instances.
Here are the questions I now ask regarding everything: What does that mean? And what does that mean to me? Learn to ask them out loud, demand the answer to your satisfaction, take the question to the 10th degree, I don't care how long that takes, now get it in writing. Asking these question before the disaster happens is a good thing. Remember, your level of expectation is higher than their level. Way higher. You can not leave them to build it like you want it and expect that it will happen.
An owner I know of built a house (not prefab), he went there on weekends to visit it. The site was prepared, the house was to be started on Monday, he came back the next weekend and it was facing a different direction. The contractor said, I thought it would look better this way. The owner was so angry, and he later sold the house.
Our friend had a pond dug in. It was all planned, and the backhoe guy knew where it was to go, it was staked out, he went back to other work on the farm and when he returned in the afternoon, the pond was in a different place. The backhoe guy said, I liked it over here better. That pond was filled in and redug at the operator’s expense. The house was never turned around.