Now this is what I mean: assuming you sold your piece of landform $20k, you use $10-13k to invest in bitcoin and the remaining $7k to buy another land somewhere at a cheap rate. Surely, with years the value of that land will always appreciate so you still have a land (only that it's at a different location) while you invest in bitcoin stead of using (risking) all the money at ones.
Just my two cents.
Your two cents worth of advice is excellent, and it will help in accelerating the creation of a well-diversified investment portfolio. In this case, having only one investment makes it very difficult to achieve your desired goal due to the numerous lapses that come with having and maintaining an investment. Bitcoin investment is good and can be relied on; however, investing your money in land for future resale or use will also yield significant profits. What matters is how you plan your life and achieve your life goals. If the method you've suggested works for you, go for it; if not, you can always try another; what's more important is to try and invest in more than one investment with your money.
For a long term investment asset like bitcoin having a some other source of income inflow as backup can be helpful in building a good bitcoin portfolio whatsoever lapses that emerges in midway you wouldn't be forced to tamper with your long term investment bitcoin plans as your other source will cover for it.
Technically, if you had to sell a property or properties to get money to invest in bitcoin it then interprets that you don't have any other money left after using all to invest, and should in the process you had to face a financial crisis that entreat an immediate financial response you may either be forced to sell your coins or sell another property again.
Assuming you divided and invested a higher percentage of the money in bitcoin and diversified the rest amount into other sort of Investment. Under such circumstance the other Investment can be used in solving your issues that's why diversification is necessary as an investor.