Are appraisals necessary for only wholesaling?

[Steven Vaughn]

If I'm just wholesaling, do I have to appraise it myself, or is it the buyer's job? Can I just use good comps and tell the seller what it is most likely worth? Or will he tell me to appraise it first. And if the house was recently appraised by a stranger(let's say only one month ago), will it show up on a record? Can I pull out recent appraisals instead of paying for it again myself?
And I heard that appraisers will know if it will be a good deal for wholesaling or not, is this true? And does it cost anything to get only advice from them instead of appraising a house?