My buyer cannot pay in full but I need to sign already a DOAS.

I have a buyer who is also a friend who offered to buy my property (house and lot). we have agreed with the price. she gave an ernest money and i was tied to sell only to her. she applied for a Pag-Ibig loan that took so long to get approved (more than a year!). finally it was approved but it was below the agreed amount, 20% short. she asks me to go on with the sale and promese to bay the remaining balance in 3-4 months. i have not signed the deed of sale yet as I am looking for any documents that i can prepare to protect myself. I don't want to be tied down for another year or worst, not being paid at all.

Is a promisory note enough? is there other legal documents i can make to secure my money or property? pls advise. I need your help.

Promissory note / MOA is enough

pwede rin ang promissory note at MOA.

but sa DAMI na ng mga kasong hindi nagbabayad, i would rather go with the old method... KALIWAAN.

you pay me the price i want, i give you the deed of absolute sale so we can register it sa LRA para ikaw na ang maging lawful owner. if you don't want, forget it. ganun lang.

or if you really care for your friend, ASK for a collateral, moving or real properties. expensive jewelries, car, gadget, etc.

to learn more about earnest money, read this po - http://www.batasnatin.com/law-library/civil-law/sales/2355-option-money-vs-earnest-money.html