Whether you are providing products and services or just products it's extremely important to think about the future of your business. It's highly unlikely your business will be the same business that it started out as in "X" years time. Some businesses will have to completely change in order to stay alive. Also if you want to increase your turnover and/or profits adding more products to your portfolio can enhance your business no end.
When you first start your business you might not have enough cash flow to buy all the products that you can sell...but you know once you have the cash flow you are going to add these future products. For example you might sell small items that don't cost a lot to begin with - but then later buy bigger ticket items that sell for more. Usually big ticket items don't usually have high margins - but you might end up with a bigger profit by selling them. Also by having bigger ticket items you can quite often sell smaller cheaper items - people can often come to your store whether it be online or a typical bricks and mortar shop to see big ticket items but then buy something for less.
There is obviously a danger in selling big ticket items - the danger being you don't sell them and you get stuck with them - you may find the product can go off or reduce in value over time or the price has fallen from where you purchased it from.
Sometimes future products aren't about being able to afford them in the future; it can be about re-branding your products. It maybe that you didn't really advertise a product you offered before very well and by giving something a change of name and bringing it to the forefront can give the awareness to your potential customers that was needed.
Future products to offer may just materialize in front of you - if something suddenly trends and you can provide the product - quite simply you just get on with it - make hay while the sunshines. These kind of products are difficult to come across you need a good dose of luck.
Many businesses don't make time to think of new products to sell. It's a good idea to have someone dedicated within your business who has a good eye for new products and whether a decent mark-up can be put on the product and still sell. Alternatively you can have a team of people who come up with an entirely new product that can go viral.
Sometimes you might want to offer a free product in order to increase the likelihood of more sales. For instance you might offer the first beer on the house. This can bring people in that wouldn't normally come as well as keep the local sweet.
If your business keeps doing the same thing then eventually someone else will offer the same product at a cheaper price or a higher quality product for the same price and then you can kiss goodbye to the business. It's really important to keep evolving your business.