Unless the house has been sitting on the market for a long while, it is, imo, doubtful that the seller will "hold" the house for you, and take it off the market, for up to 2 months while you wait to hear the outcome of your disability case.
That being said, there might be some things you can do to make yourself more attractive to the seller.
1. have an agent (I assume this is a listed property) write up the offer to show your sincere interest - even though it will be congtingent on the decision letter - having an offer in writing shows you're serious - make it a "good" offer
2. you might, as part of your offer, want to offer some non-refundable deposit as an incentive...but that's totally up to your comfort level and ability to do so
3. or - allow/ask the seller to accept your offer, but keep the home actvie on the market.......you would either have to remove your contingency if another offer comes along, before your decision letter comes in, or allow it to be sold to another buyer