JSFiddle - React, Tailwind, and code Playground

HTML

<input type="radio" name="cashcheck" value="cash" checked />Cash
<br />
<div id="cash">
    <form method="post">
        <input type="text" name="cashTxt1" />
        <input type="text" name="cashTxt2" />
    </form>
</div>

<input type="radio" name="cashcheck" value="check" />Check
<br />
<div id="check">
    <form method="post">
        <input type="text" name="checkTxt1" disabled />
        <input type="text" name="checkTxt2" disabled />
    </form>
</div>

JavaScript

window.onload=function(){
    var radios = document.getElementsByName('cashcheck');
    radios[0].onchange=toggle;
    radios[1].onchange=toggle;
};
function toggle()
{
    if(this.checked)
    {
        var div = document.getElementById(this.value),
        inputs = div.getElementsByTagName('form')[0].getElementsByTagName('*');
        for( var i=0; i<inputs.length; i++)
        {
            inputs[i].removeAttribute('disabled');
        }
        
        var op = this.value == 'cash' ? 'check' : 'cash',
        divOp = document.getElementById(op),
        divOpInputs = divOp.getElementsByTagName('form')[0].getElementsByTagName('*');
        for( var i=0; i<divOpInputs.length; i++)
        {
            divOpInputs[i].setAttribute('disabled');
        }
    }
}