If you are marketing yourself as straight and only 'gay for pay', you can - and will almost be expected to - be only the 'active' partner in anal. You will also get men paying to suck you off, without expecting you to reciprocate. This works if you're going for the posh suit niche, or the sports kit one, or the 'rather mug you than fuck you' one, or...
If you're going to sell your 'receptive anal' virginity, I'd suggest not doing it with someone on a first booking, not doing it cheaply, and practising by yourself first.