@zakariyya My suggestion would still be to not invest this money. I am not any kind of expert, so do not rely on my advice, it is entirely up to you. I know it's tough having money just sitting there and not doing anything. It sucks that interest rates on bank accounts and CDs right now are so low, they don't even keep up with inflation. That's why I suggested maxing out on I bonds.
If it were me, I simply wouldn't be comfortable with the risk of something happening in the market like it did in 2000 and 2008. I try to separate my different accounts. My long term retirement accounts, sure, I can handle that risk, since long term the market seems to continue to grow. However, for my short term goals (saving for a house, my emergency fund, saving for vacation, etc), it's just not worth the risk. I'd rather buy I bonds every year, to ensure that money is at least protected from inflation, and keep the rest in the highest yield bank account I can find.
The only other suggestion I would make is to consider if you actually want to use that money for a down payment, or if you would rather invest it in a retirement account. If you max your TSP and IRA contributions, you would be able to put $26,500 a year into retirement accounts (or $53,000 a year if you are married and contribute to your spouses). You could get that $100k into retirement accounts by the time you are out of the military, and use a no down-payment VA loan. Or you could keep enough for a 20% down-payment, and put the rest into a retirement account like I described. Lot's of options to consider, but it's ultimately up to you.