It is hard to tell if yahoo shares has reach the bottom.
Couple of ideas for you to consider:
Best - Wait until it starts to go up with decent volume, rather than try to catch the bottom now. In other words, like the trader talk, DO Not catch a falling knife.
Medium - Buy a small batch (100 shares) each time it goes down by 5% and limit your risk to 500 shares until it shows signs of up trend (see above)
Worst - Buy huge postion now (>1000 shares) and try to catch the bottom
Discipline of risk management
For short term, buy 2-3 month at the money put options to hedge your long position
Or sell deep in the money call against your long position and use part of the premium you collect to buy short term put option
If you lost 15% total of your yahoo position, start to sell at loss by batch of 200 shares for each 10% drop of the share price
Finally If the market turns due to sudden event such as war, get out the position immediately if you are not hedged
Never double down on your losing position until you see a clear and lasting up trend...There is another post about the big hedge fund losing big ($5B in 1 week) in natural gas bet or read WSJ abut this story
BTW...Please don't sell your house to buy ANY stocks
