exchanging your property with prebuilt house through dalal companies like eproperty nepal , sara sewa , property 360 , lalpurganepal is the worst decision, they depreciate your property and appreciate their pre built house by around 30-40 percent , citing mandi , recession whatever they call it . instead mobilize local dalals set them your fix price . they have a vast network n you dont have to pay a dime until you sell it . selling in this market is most diffiult part . once you sell it and have cash in hand you can buy from whoever you want. buyer has always upperhand. all house built these days are earthquake resistant so dont worry .

your problems and solutions
1.yes they will exchange your property with prebuilt home . but during exchange , massive depreciation occurs so not a good idea in general .
2. yes possible , one can send upto $50000 a year through western union each calendrer year after your Id is verified . but you can only send $ 4999 each time so need to have multiple transaction . as long as its legal money Wu , moneygram are safe .
3. there is a building protocol in nepal that every builder has to follow so they are safe . they have better design than local builders so prebuilt house is not a bad idea .
4. they give loan to nepali turn us citizen , all they look is your pay stuff and collateral in nepal . rastriya banijya bank was wiling to offer me loan upto 75 lakhs to built my house