Investing in precious metals like gold and silver, is not an investment in the sense that an investment should produce an ongoing return as interest, rent or dividend.

You should be able to keep the object of your investment and obtain an income from it.
An object that produces a capital gain return is not that kind of an investment. Anything that you have to sell, only produces a profit if you can buy it wholesale and sell it retail.

If you bought some silver cutlery for lets say 1000, and you could hire it out for 100 each time.
If you could hire it out 10 times a year, you would have a return on your 1000 investment of 1000, or 100% return on your investment per year.

Notice that you still have the cutlery and, as long as it is not damaged, you can hire it out again and again, producing more and more income from your original investmemt.

Normally, when you buy a quantity of a precious metal, you are doing it at a retail price from a dealer who buys it wholesale from you to sell it at again at retail to you.
When that happens, the profit that you think you are making, yes the price has gone up, but it just means that the currency you are selling it for, has just lost some of its value.
Because the currency is now worth less, you get more of it for the same amount of product, but the effect is that you are standing still.
Say you buy gold from another country, if its exchange rate has gone up with reference to your currency, then you need more of your money for the same value of the other currency. The weight or quantity exchanhed is the same, only the exchange rate has changed.

Say you bought an ounce of gold for 800, at retail mind you, it has gone up to 900 retail, but you would have to sell it to a bullion dealer to realize a "profit" and you can only get 850.
You think that you have made 50 profit, and you now go an buy gasoline.
Now the gasoline that would fill your tank for 40 now needs 50 for a full tank.

You also need 900 to buy another ounce of gold again at retail, but you only have 800 left (you used the 50 for a full tank of gas, remember?).
So, you now have to produce another 100 to buy another ounce of gold that you hope will increase to maybe 950, and then just repeat the fallacy.

The only one making any money is the gold bullion dealer (and this is every time you buy from him at retail and sell back to him or another dealer at wholesale price- they buy wholesale from you and sell it back to you at retail, comprende?).

Now, should you hold on to your ounce(s) of gold, you probably have to pay for storage and insurance, so, it is not producing income it is eating up costs.

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Now, if you can buy materials at wholesale price, put some work into it or maybe not, but resell them for a profit, or rent them at a rent that is income producing, well.
Say you invest to buy a machine for 1200, you now rent it out, and lets say that the cost of repairs/maintenance is 240 per year.
If you wanted a 10% return on your money, you would have to rent it out for at least 10/mth (that is 120/year), but for the repair/maintenance you would have to charge at least 20/mth (that is 240/year).
Should you want to get a 10% on the repair/maitenance as well, you would include it in the annual investment, ie: 1200 + 240 = 1440.
Now 10% of this figure is 144/year or 144/12 = 12/mth; but let's not forget that we have to get the costs back, not just its interest.
So, the amount would become a minimum of 12 + 20 = 32/mth.

If your repairs/maintenance costs were higher than expected, you could include them in the next year's charges.

Now, the machine is not going to last say more that 5 years.
In 5 years time a new machine might cost 1800 (1800 / 5 = 360).
We will need at least another 360/year to be saved for the new machine.
Now the minimum amount would be 12 + 20 + 30 or equal to 62/mth.