In real estate,the trick is accumulation and getting in at the earliest opportunity. I guess this applies to all life issues such as getting education,starting a family etc.
I assume you have the land but not enough cash to build. Besides,you have no time/expertise to build yourself.
A mortgage is desirable than savings cause the repayments are not tied to inflation. For example,if your repayment is 50K a month now,the repayment will be the same 20 yrs down the line,irrespective of the inflation rate. The value of the property will have risen. Even if you end up paying 13M,the property will probably be worth much more than that. In any case,you may be to repay the mortgage faster by making lumpsum payments from time to time.
HF has changed alot over the years mainly due to stiff competition from S&L (top dog in mortgage but have no 'Makao' type product) and banks. HF are normally not very upfront with all the details which evntually come to haunt borrowers. I would recommend you exercise due diligence particularly on the construction costs and most importantly,the monthly mortgage repayment calculation. This is where they rip where they did not sow. The fine print called 'terms and conditions' should also be thoroughly examined.
If satisfied,please go for it.
reithi