No APR. It is just a way to protect your account from being stolen instantly, in case someone manages to get your keys.
With the savings acccount, even a hacker has to wait 3 days to get access to your funds, and if you log in in the meantime you can notice the activity and change your keys.
In my opinion, the best answer is in Rich dad poor dad, and it goes like this.
First, figure out your expenses.
Then earn money, and your income has to be greater than your expenses. Save and invest as much as you can.
Your investments should provide you some income, rent from your real estate acquisitions, stock dividends, bond yields etc. Once this income is greater than your expenses, you become wealthy.
After that point, NEVER spend more than your "passive" earnings, and keep increasing your investments with the extra money.
Have you seen the splinterlands Dapp? They made hundreds of thousand of dollars in profit out of this business, and they keep growing.
It is still very hard to use HIVE and it can only get better with time, for all dapps.
Once SMTs are released, this will allow a completely new way to design dapps, by having a currency adapted to the dapp. The currency can be adapted by programming its inflation and creating the right amount of sinks to burn it.
Then, for your webapp, you can use any language you like!
Hive price started around 0.2$
After Justin Sun dumped his stake, manipulating the price, we reached 0.12$ and stayed there for a while.
Then, the Huobi listing happened, and Hive pumped to 1$, and got listed on many exchanges during that time.
Finally, it corrected back to 0.23$, and now we're at 0.25$.
If the original price you see is higer than 0.25$ this just means that the exchange you are using listed HIVE after the pump.
When you post, you can choose to earn in two different ways:
HBD are Hive-Backed Dollars. They can be sold on the market (usually trades between 1$ and 0.95$) or can be converted for 1$ worth of HIVE, which is a process that takes 3.5 days.
HP is Hive Power. Hive Power is something you get when you "power up" HIVE. "Power up" just means staking. So when you stake 1 HIVE, you get 1 Hive Power (HP). Therefore 1 HP = 1 HIVE in terms of market price. Hive Power cannot be unstaked instantly. To unstake, you need to start a "power down" which takes 13 weeks to complete. Each week you'll receive 1/13th of the amount of HP you decided to power down.
I would recommend choosing the second option, 50% HP and 50% HBD, because you'll get 50% in liquid rewards which you can sell instantly. If you don't want to sell, you can buy HIVE with the earned HBD and power up. Both methods pay the exact same amount in terms of USD.
The blockchain does not take a fee, you get paid the full dollar amount that you saw below your post. However, the dollar amount can change for up to 7 days. After 7 days, you get paid whatever is written.
The dollars earned on posts come from the inflation of HIVE. Newly created HIVE are distributed to content creators and curators (block producers and HP holders as well, but much less). The more upvotes a post receives, the higher the percentage of the total inflation the post receives. The "reward pool" is what we call the HIVE that is going to be distributed to posts.
The more HP you have, the more your vote counts in determining where the funds in the reward pool go. For instance, if someone has 10,000 HP and his vote pays out 1$ to a post when he upvotes it, this means that someone who owns 20,000 HP will have an upvote worth 2$.
Hope I answered all of your questions.