Is it risky for seller to use the same lawyer use by buyer ?
Will the lawyer side with the buyer to give unfavourable terms to the seller ?
What are the advantages and disadvantages of using same lawyer that the buyer uses ?

advantage = save money - no need to pay legal fees on SPA. Note SPA only.

Disadvantage = if you do not know what to look out for in the SPA, u might get unfavourable terms and conditions. Also, you will just have to take whatever the lawyer tells you. No way of checking whether they are screwing u or otherwise.

i find it more risky to trust the lawyer is acting on your behalf. i don't think can use the same lawyer, but can use the same law firm.

advantage: faster processing. less delay because buyer and seller's lawyer is in the same office. save cost for seller

disadvantage: need to be extra careful and check the agreement yourself. most SPA is pretty standard, if you have not seen one before, get yourself familiarized with it in case there are any tricks or unfair conditions.

honestly, whether you are appointing your "own" lawyer or requesting the assistance of the purchaser's solicitors to assist you to complete the transaction, the risk is the same and at the end of the day, all vendors are afraid of that the solicitor will run away with the money but you can be rest assured that this will not happen unless that firm of solicitors looks dodgy. practically speaking, no solicitors will risk their practicing certificate for a small amount of money, not worth it.

solicitors are generally obliged to draft the sale and purchase agreement as fair as possible but we cannot ignore the fact that there are solicitors that are "over-protective" of their client. actually, there are only a few clauses in which a vendor needs to look out for (ie. the documents that are required to be furnished, the time to furnish such documents, the time to settle the purchase price, the manner how the balance purchase price is to be released to the vendor and the consequences of purchaser's breach). the rest are almost negligible.

like all the previous posters, the obvious advantage is that you save up on quite a lot of legal fees but you still need to pay for the filing of CKHT forms and attending to the redemption of the property (if applicable).