You can typically only have one FHA loan at a time (usually must occupy as a primary for a minimum of 12 months), but there are some extenuating circumstances such as a growing family or moving to a bigger property closer to work that would enable you to apply for a second FHA loan before departing.

I’m hoping to invest in a buy & hold property using a HELOC from my primary home as the down payment.

Yes, you can use FHA and Conventional program for a primary home if you are buying a "Distressed" property - (Will not pass an inspection) "Subject to">  FHA offers a 203K loan and Fanie Mae offers a Home Style program which has the sole purpose of working with distressed properties. 

I'd reach out to someone in a local REIA where the property is located- those folks will know of some private individuals that are looking to lend. if the SFH is your primary residence, you should be able to get a HELOC at a decent rate from a regional or credit union.

They want more online leads, but I'm quickly learning their bigger issue is outbound sales & marketing, i.e. understanding who their customers (and referral partners) are and engaging them meaningfully.I've been lurking on BP and researching their build areas and it seems like their primary clients are developers and investors, not individuals building their dream vacation home (though they are part of the mix).Their value prop is dollar efficiency and speed.

Generally only one FHA loan at a time but you usually can utilize a new FHA loan for a new primary after twelve months of occupancy in the current residence. 

In some cases a primary residence makes perfect sense to rent; in others renting it becomes a big cash suck. 

My family and I are looking for a primary residence with the plan to rent it out after hopefully 5-6 years.

I was looking for a primary residence at first with no intention on it becoming an investment property.

So I have 2 questions.1) Can a bank initiate an acceleration clause because they find out your primary residence or investment property is in a LLC?