After your response to Don, I am still unclear what you are asking.
What does "monthly rate is 300" mean?
When you buy a home here in the United States (perhaps you are new to homebuying the U.S.) you make an offer on a home you want to buy for the price you want to buy it for. In your offer you also indicate that you are an earnest buyer by putting down an earnest money deposit (for a $50,000 home the earnest money deposit will likely be around $500 or $1,000). The earnest money deposit isn't cashed until the contract details have been agreed upon by both parties. The earnest money deposit also is credited to whatever "funds to close" that are due at closing, as it is funds you have contributed to the transaction. The possible "funds to close" that is needed from you will consist of your down payment amount + any closing costs that you are responsible for.
If you aren't planning on buying the home with cash, then you are going to need a mortgage in order to purchase the home. A mortgage is a loan on a home. There is an entire qualification process for the mortgage that is extremely in depth, I won't go into it because I am not even sure if you want to use mortgage financing, so it may not be information you need. But anyway if you do get a mortgage, then there is a monthly mortgage payment that is due each month. That mortgage payment is calculated using your loan amount, the interest rate you qualified for, and the term of your mortgage. A longer term, a lower loan amount, or a lower interest rate will all result in a lower monthly payment... inversely a shorter loan term, a higher loan amount, and a higher interest rate will all result in a higher monthly payment. The mortgage payment would consist of the principal & interest and may also include the property taxes & homeowners insurance.
To give you a hypothetical payment, on a $50k sales price, with a 20% down payment ($10,000), leaving $40,000 to be financed, and let's use a rate of 5% on a 30-year term, the principal & interest would be $214.73/mo. Property taxes would be estimated at $52/mo, and homeowners insurance probably estimated at $60/mo... if you chose to pay your property taxes & homeowners insurance with the mortgage portion of your housing expense, then the total payment in that example would be $326.81/mo.