Thanks for your question.
First, it will be good to know your credit score - with credit cards, your FICO credit score is more important than any collateral that you might have (i.e. a house or a land as you mentioned).
With an excellent credit, you will able to get the best credit card offers with high limit, low APR and high rewards.
Just for clarification - the limit you are asking for ($50k) is really high for a starting credit limit, unless you income is more than $500k. However, there is a way to get to that figure gradually by increasing credit limit on a card.
First, you should look at American Express credit cards - AmEx is known for its generous credit limit policy. Top tier AmEx cards - for example, AmEx Starwood preferred guest card, offer high credit limit from the account opening.
Another big plus of AmEx cards for you is their 3x credit limit increase (CLI) policy
After you get a card, and keep it in good standing for 60 days, you can apply for 3x CLI . The bank will reassess your application- consider your income, rent, payments, etc. and will make a decision about the increase. It is possible to request one 3x CLI and one 6 month after - that means that you potentially can 9x your initial credit limit in 8 months’ time frame.
Some Chase cards (Chase Sapphire preferred for example can also issue high limit cards).
With respect to an APR - you should understand that today most credit cards APRs vary depending on cardholder creditworthiness. For example, AmEx Everyday cards APR vary from 13.24% to 22.24%. It definitely pays off to have a good credit score.
On of the important questions is why you need such a high credit limit?
Credit cards limit usually is enough if you can make all your monthly spending and still keep your credit utilization under 30%. For example, if you spend $10,000 every month, it is good to have $30,000 credit limit to keep your debt utilization low.
Keep in mind that credit card is very dangerous tool if you need to make one large purchase or payment and carry a balance on the card. Credit cards is one of the most expensive form of credit, and usually getting a personal loan is much less expensive. If you have a collateral (like a land or a house) - you will be able to find quite inexpensive loan.