I do not have my own taxes done by them (my guy does not want any new business...he's on his way to retirement) but those two firms are good at investment properties and I do feel comfortable recommending them.  

As an 18 year old just starting out in wholesaling, how could I build my credibility so sellers and buyers feel more comfortable and trust me when selling/ buying a home?

It sounds like at this point your options may be to either: A) see if there are other forms of investing he could get on board with and start there to see if he grows more comfortable with time and experience or B) table the investing for now in order to preserve your marriage. 

Would they even give you a seat at the table?

Tell them to pack up their things, place them into the trunk/back seat of their car, and drive 200 yards across the complex. 

We don't have CPA yet and when we tried to consult couple of CPAs recommended to us, it was clear they have not dealt with investments and were not sure what to say, so we are not comfortable hiring them.Any clarification would be greatly appreciated!

Get a feel for what areas you'd be comfortable investing/living in if house hacking.Feel free to message me anytime with any questions, or let me know if you'd like to meet up and discuss local real estate over coffee.

Don't mistake these things for not taking action, they are critical for most people to feel comfortable to jump in, just like you would before starting any business.  

Find your comfort zone and pull the trigger.

@Lewis Anderson Are you comfortable working with your CPA remotely?