Im posting only because of the raft of YANBUs. I disagree. Totally.
There are significant elements to this that are being utterly ignored. Firstly, OP is anticipating enjoying potential shared ownership using DPs financial contribution/deposit too. This is a 2 way street.
If you were indeed able to buy the property alone, then yes Id agree with posters. But that isnt the case. This is 2 people joining financial forces to live in a nicer place than they could both afford individually. If 2 mates were buying, which is common, there is of course an understanding that if, heaven forbid, anything happened to either party, the property would be equally divided. Wills and bequests being utterly separate.
Secondly, why oh why, is everyone ignoring your financial ability to keep the property if your DP died? You wont wake up the morning after his passing, suddenly earning 3 times your current salary.
So only 2 considerations are on the table here. If you both take joint insurance to cover the joint mortgage in the event of death etc, (which you really must do), your share of that mortgage debt would also be paid off in the event of his death. (Not too shabby a position)
You would then have the choice of either, selling to meet his request of his children inheriting his share, or re-mortgaging for half the value of the property and paying the 50% value to his children. (Any lawyers here, would a joint mortgage insurance settlement become part of a deceaseds estate? Or would the estate only consist of the pre death equity?)
Worse case scenario, would you be able to raise a mortgage for 50% of the value? If you arent, then that perhaps that explains DPs position in the first place. Is it a huge discrepancy between your financial positions?.
Personally, I dont see the slightest issue in what the DP is proposing. Hes not demanding your deposit or your financial contribution is then bequested to his children if he dies, only his contribution.
If youre both matching deposits, and equally meeting the mortgage and bills, then both of you are utterly entitled to leave your estate to whom you wish.
If you are hung up on being a sole beneficiary, then youd be better served by taking out an additional death only insurance policy on DP for the value of half the property. (To cover the inheritance issue). That policy is unrelated to any property and stands alone, and you can specify that you are the sole beneficiary. The whole issue then goes away. Mortgage free plus a lump sum.
You have said you are not prepared to invest all that you have in a property that you feel isnt secure. I dont get this. Your share is, and will always be secure. It also ignores any future relationship breakdown. This is a bun fight over your partners share, in the event of his death, and ignoring the fact that hes actually paid for that share, imo is somewhat unsavoury. Are you actually stating that youll only consider buying with him if all his contributions must then come to you?
How would you feel if your DP stated that your hard saved deposit must immediately be earmarked for his (and his childrens benefit) on day one of joint ownership and infact those are the only terms that he would purchase with you? Thanks for your past 10 years of frugality. Result.
You are of course equally entitled to bequeth your share to whomever you wish and would suggest wills and additional policies are put in place to protect DPs position also.
Im curious though, What do you wish to happen if the relationship breaksdown?