What is the payback period? What is the discounted payback period?

Group Project Title: How should a normal people make the best use of a windfall?- Description: You are a student just graduate from university (22 years old) and start another chapter of life. After a period, you finally find a job and get a so-so monthly salary $3,200 per month when you are 23(because of the virus, the job market is not very good). After working 5 years in the company, your salary increase to $5,000 per month. You want to retire when you are 60 and leave no coin when you are 80. Luckily, you won the lottery ticket, though it is not a huge amount ($60,000). And you start to think about how to make the best use of it. Option 1: You prepare to use the money to buy a house in Calgary and rent it to international students. House price is $450,000 with 20% down payment. When you retire, you will live in this house and get a periodic payment ($4,000 per month). Before that, you choose to rent a house too ($450 for rent and $50 for internet and others fee). All the money you earn will be deposit in the Scotiabank which offers you 2.5% interest rate and compound monthly. In order to buy the house, you prepare to run a ten-years mortgage and make constant monthly payment. Group Project Title: How should a normal people make the best use of a windfall?- Description: You are a student just graduate from university (22 years old) and start another chapter of life. After a period, you finally find a job and get a so-so monthly salary $3,200 per month when you are 23(because of the virus, the job market is not very good). After working 5 years in the company, your salary increase to $5,000 per month. You want to retire when you are 60 and leave no coin when you are 80. Luckily, you won the lottery ticket, though it is not a huge amount ($60,000). And you start to think about how to make the best use of it. Option 1: You prepare to use the money to buy a house in Calgary and rent it to international students. House price is $450,000 with 20% down payment. When you retire, you will live in this house and get a periodic payment ($4,000 per month). Before that, you choose to rent a house too ($450 for rent and $50 for internet and others fee). All the money you earn will be deposit in the Scotiabank which offers you 2.5% interest rate and compound monthly. In order to buy the house, you prepare to run a ten-years mortgage and make constant monthly payment